Lab Test Book CHT

Lab methods for judgement of pretreatment

Our department for applied technique is always at your service for further information and advice.

Our technical advice and recommendations given verbally, in writing or by trials are believed to be correct. They are neither binding with regard to possible rights of third parties nor do they exempt you from your task of examining the suitability of our products for the intended use. We cannot accept any responsibility for application and processing methods which are beyond our control.

If producers or sources of different chemicals are mentioned for evidence reaction tests, it is done without evaluation. It is impossible to take into account all chemical producers in such an infomation brochure.

Our department for applied technique is always at your service for further information and advice.

Our technical advice and recommendations given verbally, in writing or by trials are believed to be correct. They are neither binding with regard to possible rights of third parties nor do they exempt you from your task of examining the suitability of our products for the intended use. We cannot accept any responsibility for application and processing methods which are beyond our control.

If producers or sources of different chemicals are mentioned for evidence reaction tests, it is done without evaluation. It is impossible to take into account all chemical producers in such an infomation brochure.

evidence ............................ ............................ ........................... ........................... .................1 ...1 Methods of evidence.............. Chemical damaging damaging of cellulosic fibres................. fibres....................... ............ ............ ............ ............ .......... .... 1 Qualitative evidence for iron.................................................................... 2 Qualitative evidence for hydro- or oxycellulose oxycellulose ....................................... 2 Qualitative Qualitative evidence of hydrocellulose hydrocellulose with silver nitrate ............ .................. ............ ...... 2 Qualitative evidence of oxycellulose with methylene blue....................... 3 Qualitative evidence of damaged cotton by swelling test (immaturity control by swelling test)........................................................................... test) ........................................................................... 3 Evidence Evidence of fats and oils on the fabric ............ .................. ............ ............ ............ ............ ............ .......... .... 4 Red-green test ........................................................................................ 5 Determination of absorbency .................................................................. 6 The degree of desize – the TEGEWA-violet scale................. scale....................... ............ ........... ..... 8 pH- value on the fabric ............................................................................ 9 Conductivity test...................................................................................... test ...................................................................................... 9 Evidence of non ionic residual surfactants............................................ surfactants ............................................ 10

Identification of fibre materials............. materials ........................... ............................ ..........................12 ............12 Hydrogen peroxide ........................... ......................................... ............................ ............................ .................16 ...16 Properties of commercially available H 2O2-solutions -solutions ............ .................. ............ .......... .... 16 Storage Storage and storage life of hydrogen hydrogen peroxide ............ .................. ............ ............ ............ ........ 16 Stoichiometrical calculation of the active content in H 2O2-solut -solution ions s .... ...... 17 Analysis of H2O2-content in bleaching baths......................................... baths ......................................... 17 Analysis of H2O2-content on fabric ........................................................ 20 Semi-quantitative analysis of hydrogen peroxide content with titanyl chloride.................................................................................................. 22 Semi-quantitative analysis of hydrogen peroxide content with Merck-test rods ..................................................................................... 24

Alkali............ Alkali .......................... ............................ ............................ ............................ ........................... ........................... ...............25 .25 Analysis of alkali-content in liquors ..................................................... 25

Sodium hypochlorite (chlorine (chlorine bleach lye) lye) .............. ............................ ...................27 .....27 Properties of commercially available chlorine bleach lye ............................ .............. ...................... ........27 27 Reactions of sodium hypochlorite ............................ .............. ............................ ............................ ............................ ...............27 .27 Active chlorine chlorine .................... .............................. ..................... ..................... ..................... ..................... .................... ..................... ..................28 .......28 Analysis of active chlorine content in sodium hypochlorite hypochlorite bleaching liquors liquors ......28 Dechlorination.....................................................................................................30

Sodium chlorite .......................... ........................................ ............................ ............................ ........................32 ..........32 Properties of commercially available sodium chlorite..........................................32 Reactions of sodium chlorite...............................................................................32 Analysis of sodium chlorite content in bleaching baths ............................. ............... ........................ ..........33 33 Destruction of residual chlorite............................................................................36

Persulphates ..................................................................................37 Properties of persulphates ................................................................................. 37 Analysis of persulphate content in addition to hydrogen peroxide in bleaching baths.................................................................................................................. 37

Silicates .......................................................................................... 41 Properties of commercially available silicates of sodium.................................... 41 Properties of commercially available metasilicates ............................................ 41 Other properties of silicate of soda..................................................................... 41

Water hardness.............................................................................. 44 Analysis of water hardness (total hardness)....................................................... 46 Conversion factors in common units for water hardness .................................... 47

Average polymerisation degree (DP-value) ................................ 47 Fluidity F......................................................................................... 49 Annex.............................................................................................. 50 Density and concentration of sulphuric acid, hydrochloric acid, nitric acid, caustic soda and caustic potash solution ....................................................................... 50 Brief instruction - titration of hydrogen peroxide ................................................. 56 Brief instruction - titration of caustic lye.............................................................. 57

Methods of evidence

Methods of evidence Pretreatment exerts a strong influence on all following processes, like dyeing, printing etc. Mistakes made in pretreatment can hardly be corrected or even not at all in later processes. The following simple test methods help to determine mistakes prior to processing or to obtain the chemical evidence for them so that damaging effects can be avoided.

Chemical damage of cellulosic fibres Cellulosic fibres can be chemically damaged by different influences, such as

• • •

catalytic damage during hydrogen peroxide bleach caused by heavy metal contamination. damage by contamination of fabric with concentrated acids, mostly mineral acids like hydrochloric or sulphuric acid. damage by insufficiently stabilized hydrogen peroxide bleach.

Such damages become visible by holes or by a general reduction of tear strength or the DP value (average polymerisation degree). The so-called catalytic damage is a problem of pretreatment which quite often occurs. It is caused by the presence of heavy metals, which have a catalyzing effect in peroxide bleach and promote a spontaneous peroxide decomposition and finally fibre damage.

Holes caused by catalytic damaging

In addition to copper and manganese, there is mostly iron or rust in pretreatment coming from the greige goods itself or introduced onto the fabric e.g. by the following reasons

• • •

Metal abrasion during storage or transport of fabric. Rusty pipelines or machines parts in the pretreatment plant. Contamination of the industrial water with heavy metals.

The presence of iron on fabric or in industrial waters can be proven rather easily.

èq=oK=_bfqifè=dj_e=

1

Methods of evidence

Qualitative proof of iron Ammonium thiocyanate (NH 4SCN) forms a very red complex with iron. This proof can be obtained directly on the fabric or as well as in aqueous solutions.

Procedure The fabric sample is treated with a solution of 1-2 spatula tops of ammonium thiocyanate (NH 4SCN) in approx. 10-15 ml hydrochloric acid of 10%. A very red iron thiocyanate complex is formed if there is iron.

Undamaged cellulose CH2OH

OH

Qualitative proof of hydro- or oxycellulose

CH2OH

O

O O

OH

OH

O

O OH

OH

CH2OH

OH

Hydrocellulose CH2OH

CH2OH

OH OH C

OH

O

OH OH

H

OH

O

O

C

OH

O H

OH

CH2OH

Oxycellulose CH2OH

O

CHOH

CH

OH

O

CH2OH

HC

CHOH

COOH

O OH

O

CH2OH

OH

Damaged cellulose forms hydro-and oxycellulose at the damaged parts and this can be proven by simple means. Independently from the reason for the damaging, that means by acid or oxidation agents, a mixture of hydro- and oxycellulose is formed. By means of the following reactions of evidence it is indeterminate whether the damaging was caused by oxidation agents or acids.

COOH

OH

Qualitative proof of hydrocellulose with silver nitrate The hydrocellulose with the reducing effect separates elementary silver from a silver nitrate solution, and this becomes visible at the damaged parts by a yellow brown to black dyeing.

Procedure The degreased sample free of size and finish is treated for some minutes at 80°C in an ammoniacal silver nitrat e solution. èq=oK=_bfqifè=dj_e=

2

Methods of evidence

Then it is rinsed with distilled water and with diluted ammonia solution.

Production of the ammoniacal silver nitrate solution A solution of 10 g silvernitrate in 100 ml water is mixed carefully with a ammonia solution of 10 % until the white sediment which had been formed is dissolved again.

Qualitative evidence of oxycellulose with methylene blue The basic dye methylene blue strongly dyes oxycellulose very much because of the carboxylic groups and the depth of the dyeing corresponds to the degree of the damage.

To note: Merzerised CO reacts like damaged CO. Caution is advised.

Procedure The degreased sample which is free of size or finishing is dyed in a hot and aqueous methylene blue solution of 0.1% at 60 °C for 5 min. Then it is washed with boiling distilled water until there is no dye left.

Qualitative evidence of damaged CO by swelling test (immaturity control by swelling test) Undamaged CO fibre pieces treated with caustic soda show a phenomena which looks like mushrooms at the fibre ends under the microscope. However considerably chemically damaged CO fibre do not show such characteristic phenomena.

To note: The swelling reaction can be done successfully only on CO fibres. Mercerised CO reacts in the same way as damaged CO. Caution is advised.

Because of this it is possible to distinguish chemically damaged fibres from mechanically damaged ones.


3

Methods of evidence

Undamaged CO

Procedure Fibres are taken from damaged and undamaged parts of a sample. Th cotton fibres are cut vertically to the fibre direction in pieces of 2 to 3 mm with some sharp-edged scissors or a razorblade. They are put on an object holder, covered with a cover glass, and caustic soda of 10 to 15% is added from the side by means of glass capillary.

Damaged CO

The fibres are compared under the microscope by transmitted light and magnified as large as possible.

At the undamaged CO there are phenomena looking like mushrooms at the fibre ends. Chemically damaged CO does not show such "mushroom" phenomena, or only to a small degree.

Evidence of fats and oils on the fabric Ceres red 7B corresponds to Color Index Number C.I. 26050.

Fabric free of oil or fat

Residual oils and fats on the fabric often coming from preperations can have disturbing effects during dyeing e.g. resist effects. The evidence of fats or oils can be provided by a fat dye Ceres red 7B.

Procedure Fabric with oil stripes

The Ceres red stock solution is diluted with water at a ratio of 1:9 just before the application. This dilution is the utility solution. The fabric which is to be analyzed is treated with the utility solution at 60 °C at a liquor ratio of 1:60 for 5 - 10 minutes. Then wash off cold for approx. 1 min, dry and fix the dye at 150 °C for 3 min. The fats which are on the fabric are dyed in an intense red shade.


4

Methods of evidence

Production of Ceres red stock solution Ceres red 7B CHT-DISPERGATOR SMS

0.4 g/l 1.0 g/l

The dye and the dispersant are ground in a plate and pasted with cold soft water. The solution is filled up with soft water at 1 l. With time, the Ceres red dye precipitates to the bottom of the container. Therefore the solution has to be shaken or stirred before it is applied.

Red-green test Analysis of effects of caustification and mercerisation of CO and CV and of ripe and unripe CO Variations in the degree of caustification and mercerisation lead to differences of dyeability and colour depth. The following test helps to recognize such differences. If a fibre sample is treated in a solution with both direct dyes of Tubantin red 8BL conc. and Tubantin green BL highly concentrated (BEZEMA AG), mercerised materials are dyed from grey to green. This is because of the affinity differences of dyes, depending on the degree of caustification and mercerisation, and the materials which have not been treated with lye become red.

Differences of degree of caustification and mercerisation S od ium ch loirte 30v o l.% so lu tio n S h o rtnam e

not caustified

N 30

rx.24 5(=2 45 .) N al g[/k g] apo co nc en trati g[ ]l/ 300

100 g/l NaOH 100 %

silghtlyg e renisy h -ellow cl A s p e c t q ilud i 3 D en sity(20)g[c/ ] 22 m 1

S o lu b ilityinw ae ta rt

150 g/l NaOH 100 %

unlim ited

[° ] a S a trto fcrya s tlisaito nC po rx.-15

200 g/l NaOH 100 %

R eatcion alka line p (H v-aluea po rx .1

The red-green-test can be applied to differentiate between ripe and unripe CO. The ripe fibres are dyed red in the test and the unripe green.

Dead CO

Dead CO fibres are dyed much less or not at all. They can be recognized as well by their neppy agglomerations in the fibre texture.


5

Methods of evidence

Procedure The CO sample is wet-out well with boiling distilled water and then treated with the following dyeing recipe: TUBANTIN red 8BL conz.

120 110

C.I. Direct red 81

TUBANTIN conc.

green

Liquor ratio 1:40

45 min at 98 °C

100

BL

] C ° [ e r u t a r e p m e T

highly

C.I. Direct green 26

90 80

add fabric at boiling temp.

70 60

take out after 15 and 30 min and add 2.5 % NaCl (normal salt

50 40 30 20

0.8 % TUBANTIN red 8BL conc. 3.2 % TUBANTIN greenBL hightly conc.

10 0 0

10

20

30

40

50

60

Time [min]

After dyeing rinsing is carried out as follows (liquor ratio 1:40): -

2 times rinse cold 1 time rinse for 30 s with boiling water 2 times rinse cold

Then dewater the sample and air dry it.

Analysis of absorbency For more details TEGEWA-drop test:

see

„TEGEWA-drop test – a method for a rapid determination of textile absorption“ „Melliand Textilberichte 68 (1987), 581-583

The textile absorption or hydrophilic effect is mostly analyzed by the following two methods:

• •

TEGEWA-drop test Capillary rise method

The TEGEWA-drop test is usually applied for the rapid determination of the absorbency. In case of small differences of absorbency and if the best possible absorbency is necessary for the further transformation of the textile, the more complicated capillary rise method is advantageous.


6

Methods of evidence

TEGEWA-drop test – brief description

Alternative for Patentblau V ERKA Typ S 4030

The test material is put into the tension device and a drop of aqueous patent blue of 0.2 % is applied. As soon as the drop touches the test material, time is measured. As soon as the shiny surface of the drop is no longer visible, time measuring is stopped.

Ringe Kuhlmann GmbH & Co KG Hamburg, Germany

Evaluation criteria are the following:

• • •

sinking time of the drop spread diameter of drop. picture of flowing. Jagged borders of the drop can indicate woven fabric e.g. on irregularly distributed residual deposits of size, warp waxes etc.

Good pretreatment

Bad pretreatment

Capillary rise procedure – brief description There are different variations of the capillary rise procedure, and the two most important are mentioned in the following. Strips of approx. 3 x 25 cm in warp and weft direction (or in longitudinal or transversal direction) are taken out and hung in water colorated with dye (e.g. solution V of patent blue 0.2 %).

Variation 1 (DIN 53924) 40 mm

As soon as the sample is immersed in the liquid, the capillary rise is taken in mm after 10, 30 and 60 s from mark A at the liquor surface.

30 mm

C

20 mm

Variation 2

B

10 mm

Wait until the liquid level is at a height of 10 mm (mark B) and take time until mark C at 20 mm is obtained.

A


7

Methods of evidence

See further details TEGEWA-violet scale:

„The Violet Scale, a criterion for assessing the desizing degree of starch-sized fabrics“ Textil praxis international (1981), 1331-1332, 1349-1350

The degree of desize – the TEGEWA-violetblue scale

to

12

Because there is a relation between the colour intensity of the iodine starch complex and the residual starch content on the fabric, the colour reaction of starch and free iodine is applied to judge in a semi-quantitative way the residual size content or better the residual content of starch after the pretreatment. Procedure A fabric sample of approx. 4 x 4 cm is laid for one minute into a iodine solution at a concentration c = 0.005 mol/l, rinsed with cold water for a short time and then dapped off with a starch free filter paper and compared immediately with the TEGEWAviolet scale.

Remark A complete description of the evidence of sizes is at disposal in a separate CHT brochure

Evaluation 9= completely goo desized

good

average

good

bad

The mark 9 on the scale indicates a complete starch elimination, and mark 1 an insufficient one.

Fabrication of the iodine solution

Remark Because of the volatility of the iodine, iodine solutions should always be kept in a brown flask closed with a ground-in stopper.


8

To produce the 0.005 mol/l iodine solution preferably readymade solutions (e. g. Fixanal or Titrisol) are applied at a concentration of c(I 2) = 0.05 mol/l (= 0.1 N). Of this solution 50 ml are taken and filled up to a litre with distilled water.

The solution itself can be made as follows: 10 g potassium iodide are dissolved in 100 ml of water, 0.65 g of iodide are added and agitated until complete dissolution. Then filling up with distilled water up to 1 l.

Methods of evidence

pH value on the fabric

Morapex A (Habotex)

The pH value on the fabric is determined by the following method:

• • •

According to DIN EN 1413. The sample is extraced in cold distilled water for 2 h at a liquor ratio of 1:50 and then the pH is measured in the extract. With Morapex extraction. The sample is extracted with hot distilled water at the Morapex and then the pH measured as well in the extract. Dropping of a pH-indicator directly on the sample.

pH-value determination description

with

pH-indicator

–

pH-Indicator (Merck) pH 3.5

brief pH 6.5

The easiest method is the pH-determination by dropping a pHindicator (e.g. of Merck) directly on the sample. This procedure does not give absolutely reliable results, but at least a rough estimation about the pH on the fabric. pH 8

The sample is moistened with distilled water, and then the pHindicator is dropped on. Then it is compared with the colour scale.

Determination of the conductivity The electrolyte content (residual alkali, neutralisation salts and others) of a pretreated material has an important influence on the print result of a pigment printing. A high electrolyte concentration leads, for example, to a decrease of the printing paste viscosity, and therefore to an increasing and thus unwanted penetration of the print. A measure for the electrolyte content of a fabric is the electrical conductivity which can easily be determined.

Conducting meter

high conductivity (180 µS/cm)

low conductivity (20 µS/cm)

Procedure

Print side

Print side

4.00 – 10.00 g of the test fabric are weighted in a round-bottom flask of 250 ml, distilled water is added at a liquor ratio of 1:20, and the solution is boiled for 1 h by reflux. After cooling and filtering, measurement of the conductivity of the extract by means of a conducting meter.

Back side

Back side

The measuring value is given in µS/cm or mS/cm. èq=oK=_bfqifè=dj_e=

9

Methods of evidence

Evidence of non ionic residual surfactants Precipitations of a reactive dye with a non ionic surfact

Some reactive dyes (mostly turquoise types) react sensitively in the presence of non ionic surfactants which had been unsufficiently eliminated from pretreatment. If non ionic residual surfactants are suspected to be the reason for a problem, their presence can be proven in the extract after extraction of the fabric in cold water according to the so-called Draggendorff-reaction.

Procedure Example series of concentrations of a non ionic surfactant Concentration in % on weight of fabric (LR 1:20)

Concentration in g/l

0.0

0.0

0.04

0.02

The material to test is extracted at a liquor ratio of 1:20 with cold distilled water at 5°C for 5 minutes (e.g. in beaker). It is important that the temperature of the water is approx. 5 °C; because it guarantees that the non ionic surfactants are removed from the fabric to the water phase extract quantitatively. 10 ml of the extract are prepared in a test tube. Then 2 ml of Draggendorff-reagent are given to the extract, and the test tube is agitated. The orange deposit is absorbed through stainless steel filter, and the filter paper is dried.

Judgement

0.10

0.05

0.20

0.10

The intensity of the desposit is a measure for the concentration of the present non ionic surfactant. Depending on the chemical base of a surfactant precipitations of different intensity can result, and therefore a series of concentrations of the applied surfactants should be produced for comparative purposes and to allow a semi-quantitative result by this. 10 ml of every different surfactant solution is mixed with the reagent and filtered.

0.30

0.15

Fabrication of the Draggendorff-reagent The ready-made Draggendorff reagent can be applied only for a limited time, and therefore it is best to produce two different stock solutions (A and B), which are mixed just before their application.


10

Methods of evidence

Solution A: 1.7 g of bismuth nitrate are dissolved in 20 ml of pure acetic acid. After addition of 80 ml of water, a solution of 40 g of potassium iodide, 100 ml of distilled water and 200 ml pure acetic acid are filled up to 1000 ml in a graduated flask.

Solution B: A barium chloride solution of 20 % in distilled water

Ready-made reagent: Mix 2 volume parts of solution A with 1 volume part of solution B.


11

Identiification of fibre materials

Identification of fibre materials For a quantitative analysis of the fibre materials on natural or synthetic basis and their mixtures there are instructions of analysis at disposal in the technical literature.

Remark In case of fibre mixtures caution is advised. Mixed pH values might turn up and the identification becomes difficult. Preliminary tests should be burning test and dry distillation.

Natural and man-made fibres

Burning test Dry distillation

To identify the individual fibres there are different qualitative rapid methods like burning test, dry distillation, dyeing reaction, microscopical analysis or dissolution in acids, alkali, organic solvents. Burning test and dry distillation For the burning test the fibre which is to be analyzed is held into the flame, and the criteria of burning, fume, odour and residue are judged. In the dry distillation the fibres are heated in a dry test tube, and the vapours are tested on their pH value by means of a moistened pH paper. Fibre

Vegetable fibres like cotton, linen, hemp, viscose Animal fibres, like wool, silk Acetate fibres

Polyester fibres

Polyamide fibres


12

Burning test Odour

Burning, residue

of burnt paper

burns down fast, white grey ashes

burns slowly, white grey ashes burns fast, burnt-out particles with sour, like acid subsequent white grey ashes melts and burns, sweetish and sooting only in flame, stinging glassy, ropy melt, black enamel pearl goes on melting and slightly of burning without sooting, burnt hair glassy yellow to brown, ropy melt of burnt hair

Dry distillation pH-value

pH 5-6 pH 9-10

pH 2-3

pH 3-4

pH 10-11

Identification of fibre materials

Fibre

Burning test Odour

Polyacrylonitrilefibres

sweetish

Polyurethanes

malodorous

Polyethylene fibres

like burning candle

Polypropylenefibres

like burning candle

Burning, residue melts and burns, then soots, black and brittle melting residue melts and goes on burning, without sooting, black, hard and brown metling residue melts and goes on burning without sooting, light brown and brittle melting residue melts but does not burn, white smoke, yellowish melt

Dry distillation pH-value

pH 10-11

pH 10-11

pH 5-6

pH 6-7

Dyeing method The dyeing method with special dye reagents can be applied without any problems, and allows a good to rough evaluation depending on the material which is to be analyzed e.g. fabric out of one fibre kind, mixed articles of singular or uniform fibres. This does not work on dyed material, and therefore coloured fabric has to be stripped before testing. The dyeing method serves only as a preliminary test because it can be applied only under certain conditions on stripped or pretreated fabric. Special fibre material reagents for the analysis of fibre materials are offered under the name of „Neocarmin“ by the company FESAGO Chemische Fabrik Dr. Gossler, 69207 Sandhausen. The producer supplies colour scales for identification together with the reagents. Analysis of man-made fibres For a uniform fibre mixture, dyeing reactions or burning tests are not sufficient to identify singular components. A classification is possible only by a process of separation with different dissolving tests with organic or inorganic chemicals.

Man-made fibres


13

Identiification of fibre materials

The following dissolving behaviour in different solvents describes only the qualitative analysis. There are further methods in technical literature for the quantitative determination. Dissolving behaviour e t a t e c A

e t a t e c a i r T

6 . 6 e d i m a y l o P

6 r e e t d i s m e y a l y o l o P P

e l i r t i n o l y r c a y l o P

e n a h t e r u y l o P

e n e l y p o r p y l o P

e n e l y h t e y l o P

s r s

s r s

s r s

s

r s

s q s

s q q

Acetone Dimethylformamide Dioxane o-Dichlorobenzene Phenol 40% Xylol

u u u

r u

s s s

q u s

s u s

s u s

s u s

r r s

s q s

r r s

r q r

r q r

Formic acid (98%) Pure acetic acid Hydochloric acid conc. Sulphuric acid conc. KOH 40%

u u u u s

u u u u s

u r u u s

u r u u s

s s s u v

s s s u s

r q v u v

s s s q q

q q q q q

u cold soluble r soluble at boiling temperature s insoluble q insoluble, but changes during boiling v swells and decomposes during boiling

partly soluble during boiling

Natural fibres

Analysis of natural fibres

A rapid analysis of singular cellulose fibres e.g. cotton, viscose or protein fibres like wool and silk cannot be taken for granted, especially not if it is a uniform fibre mixture. Dyeing reactions and a microscopical analysis mostly can give an indication, but for singular determinations sometimes complicated wet chemical analyses have to be carried out (see technical literature).


14

Identification of fibre materials

As simple examples can be mentioned

Vegetable fibres Animal fibres

Burning test Dyeing test

Mercerised not mercerised cotton

Microscopical analysis Red-/green test

Ripe and unripe cotton

Red-/green test

Cotton regenerated cellulosic fibres

Microscopical analysis Dyeing method

Cotton Bast fibre

Microscopical analysis

Wool Silk

Dissolving tests microscopical analysis dyeing method

Pure silk (bombyxs mori) and wild (e.g. Tussahsilk) silk

Dissolving tests

Different procedures of analysis

Vegetable fibre: odour of burnt paper Animal fibre: Odour of burnt hair Not mercerised: typical corkscrew like twists of the fibre; kidney shaped cross-section Mercerised: smooth fibre, round cross-section Ripe cotton fibre: red dyeing Unripe cotton fibre green dyeing Cotton: typical cork-screw like twists of the fibre Regenerated cellulosic fibre: smooth fibre Different longitudinal section pictures of the fibres Wool: dissolves during boiling in NaOH of 5%, typical scales layer Wild silk: dissolves only partly even if boilt for a longer time Pure silk: dissolves during boiling in HCl conc. (after approx. 60 sec.) Wild silk: dissolves only after boiling for a longer time


15

Hydrogen peroxide

Hydrogen peroxide Chemical formula: Molar mass:

H2O2 34.02 g/mol

Properties of commercially available H2O2solutions Short name

W 30

W 35

W 50

W 60

[% by weight]

30

35

50

60

[Vol.-%]

111

132

199

249

[g H 2 O 2 /kg]

300

350

500

600

[g H 2 O 2 /l]

334

396

598

745

[% by weight]

14. Jan

16. Mai

23. Mai

28. Feb

1.114

1.132

1.195

1.241

H2O2 -concentrations

Aktive oxygen Peroxides have -O-O- groups, of which an oxygen atom can easily be separated as „active oxygen“ . (For calulation see below)

Active oxygen content Density (ρ20) Acid content

3

[g/cm ]

+

0.5 - 5 mmol H /l

Storage life and storing of hydrogen peroxide Decomposition of H 2O2 H2O2 (liq.) → H2O (liq) + ½ O 2 (g.)

∆H = -98.31 kJ/mol

In presence of catalytic substances hydrogen peroxide easily decomposes in an exothermal reaction to water and oxygen. Stability of hydrogen peroxide is influenced by:

•

Heavy metals (Iron, copper and manganese even in smallest concentrations reduce very much the hydrogen peroxide stability).

•

pH-value (The best pH value is between 3.5 and 4.5)

•

The concentration of hydrogen peroxide (The higher the H 2 O2 -concentration is, the more decomposition tends to diminish).

• • •

Temperature (At a higher temperature of about 10 °C, the reacti on speed increases at a factor of 2.2).

Influence of light (Hydrogen peroxide should be stored in containers which are impervious to light).

•

Other soilings (Soiling of any kind reduces substantially the stability of hydrogen peroxide).


16

Hydrogen peroxide

For the above mentioned reasons hydrogen peroxide should be protected from light and stored in its original containers or special tanks.

Stoichiometric calculation of active oxygen content in H2O2-solutions For the determination of the active oxygen content the bimolecular decomposition reaction of hydrogen peroxide is taken as basis: H2O2

→

H2O

+

½ O2

34.0146 g/mol

→

18.0152 g/mol

+

½ · 31.9988 g/mol

Example 1 How much active oxygen in g/kg does a H2O2-solution of 50% contain ?

Out of 34.0146g H 2O2 100 % result from ½ · 31.9988g = 15.9994g of so-called active oxygen.

Active oxygen = 50 · 4.704 = 235g/kg = 23.5%

The conversion factor of % by weight of H 2O2-solution in active oxygen is the following:

Example 2

% by weight H2O 2 − sol. ⋅ 15.9994 ⋅ 10 Active oxygen [g/kg sol.] = 34.0146

= % by weight H2O 2 − solution ⋅ 4,704 In bleaching baths normally the total content of hydrogen peroxide is determined and not the active oxygen content.

How much active oxygen does a bleaching bath with 10ml/l H2O2 50% (density ρ20 = 1,132 3 g/cm ) contain? 10 ml H2O2 50% contain 10 ⋅ 1.132 = 11.32 g H2O2 50% or 11.32g H2O2 50% /1000ml x=

4.704 ⋅ 50 ⋅ 11,32

= 2.7 g/l 1000 Aktive oxygen content = 2.7 g/l

Determination of H2O2-content in bleaching baths The hydrogen peroxide content can be determined by titration with potassium permanganate (permanganometrically) or with iodine (iodometrically). Titration with potassium permanganate certainly is the most often used method, and therefore it is the only procedure which is mentioned here.


17

Hydrogen peroxide

Permanganometric determination of H2O2 Reaction of H 2O2 with KMnO4 -

+

5 H2O2 + 2 MnO4 + 6 H → 2+ 2 Mn + 5 O2 ↑ + 8 H2O

Titration with potassium manganate in sulphuric acid solution is often running from colourless to slightly pink. The equivalent mass ratios result from the reaction equation or equivalent numbers of potassium permanganate and hydrogen peroxide. Equivalent number z

Molar mass

Hydrogen peroxide

2

34.0146 g/mol

Potassium permanganate

5

158.034 g/mol

The equivalent ratios result from: n(eq) (KMnO 4 O2 ) 4 ) = n(eq) (H 2 2 O 2 n (KMnO 4 ) ⋅ z (KMnO 4 ) = n (H 2 O 2 ) ⋅ z(H 2 O 2 ) = n (KMnO 4 ) =

m (H 2 O 2 ) ⋅ z (H 2 O 2 ) M (H 2 O 2 )

m (H 2 O 2 ) ⋅ z (H 2 O 2 ) M (H 2 O 2 ) ⋅ z (KMnO 4 )

Normally a solution of 0.02 mol/l (= (= 0.1 N) KMnO 4 4 is applied. Then the following equation is valid: 0.02 mol KMnO 4 =

m (H 2 O 2 ) ⋅ 2 34.0146 g/mol ⋅ 5

0.02 mol KMnO 4 ⋅ 34.0146 g/mol ⋅ 5 2 m (H 2 O 2 ) =1.7007 g m (H 2 O 2 ) =

According to this 1 ml of a solution s olution of 0.02 mol/l (= 0.1 N) KMnO 4 - - exactly corresponds to 0.0017 g H 2 O2 100 %. 2 O 2

Normally a solution of 0.1 N (= 0,02 mol/l) potassium permanganate is applied for titration. However special solutions can be applied as well, e.g. for the AATCC test 102 a solution of 0.588 N or for Europe a solution of 0.23 N. The main reason for these special solutions is a direct relation between consumption of potassium permanganate and the hydrogen peroxide concentration. The consumption of a 0.23 N potassium permanganate solution in case of a sample of 10 ml just gives the content of ml/l H 2O2 35%. èq=oK=_bfqifè=dj_e=

18

Hydrogen peroxide

Procedure of titration

Remark:

An aliquot part is taken, normally 1 to 10 ml of the bleaching bath and given into an Erlenmeyer flask containing approx. 10 ml of a sulphuric sulphuri c acid (20%). The titration is carried out immediately with the potassium permanganate solution to a faint pink colour.

In the annex, there is a very much simplified variation of the titration instruction.

Calculation The variables applied for calculation are the following ones:

V

Consumption in ml of a KMnO 4 solution at a concentration of x mol/l.

x mol/l KMnO4

Concentration of the applied potassium permanganate solution, normally 0.02 mol/l = 0.1 N

F

ml of taken quantity of bleaching liquor

ρ

Density of hydrogen peroxide solutions (H2O2 35%ig = 1.132; H2O2 50% = 1.195)

W

% by weight of hydrogen peroxide solution

The following calculation formula are such that calculation can be done with every concentration of potassium permanganate solution and every concentration of hydrogen peroxide. Normally a 0.02 mol/l = 0.1 N of potassium permanganate solution is applied.

Calculation of H2O2-concentration in g/l: g/l H2O2 x − % =

=

x mol/l KMnO 4 ⋅ 5 ⋅ 34.0146 ⋅ V ⋅ 100 2 ⋅ F ⋅ W x mol/lKMnO 4 ⋅ 8503.65 ⋅ V F ⋅ W

1 ml 0.02 mol/l KMnO4 = 0.0017g H2O2 100%

Example For titration of F = 10ml bleaching liquor with 0.02mol/l KMnO4-solution (= 0.1 N) are used V = 8.5ml KMnO4solution. How much of H2O2 50% (W=50) in g/l does the bleaching liquor contain ? g/l H 2 O 2 50% =

0.02 ⋅ 8503.65 ⋅ 8,5 10 ⋅ 50

g/l H2O2 50% = 2,89g/l


19

Hydrogen peroxide

Example For titration of F = 10ml of bleaching liquor with 0.02 mol/l KMnO4-solution (= 0.1 N) V = 8.5 ml KMnO4-solution are consumed. How much H2O2 50% in ml/l (W=50, ρ=1.195) does the bleaching liquor contain? ml/l H 2 O 2 50% =

Calculation of H2O2-concentration in ml/l: ml/l H2O2 x − % =

x mol/l KMnO4 ⋅ 5 ⋅ 34,0146 ⋅ V ⋅ 100 2 ⋅ F ⋅ W ⋅ ρ

=

x mol/l KMnO 4 ⋅ 8503,65 ⋅ V F ⋅ W ⋅ ρ

0.02 ⋅ 8503.65 ⋅ 8,5 10 ⋅ 50 ⋅ 1.195

ml/l H2O2 50% = 2,42 ml/l

Determination of H 2O2-content on the fabric To verify the application of chemicals during impregnation processes the hydrogen peroxide content can be determined directly on the fabric in a quantitative way. Procedure A piece of approx. 2-3 g is cut out of the fabric after impregnation and given immediately into an Erlenmeyer flask containing approx. 100 ml of an sulphuric acid of 20%. With the potassium permanganate solution titration is done up to first persisting violet dyeing. Then the sample is taken out of the flask, rinsed briefly with water, dried and weighted. Calculation The parameters of calculation are the following:

V

Consumption in ml of KMnO 4-solution with a concentration of x mol/l.

x mol/l KMnO4

Concentration of the applied potassium permanganate solution, normally 0.02 mol/l = 0.1 N

M

Mass of taken sample in grammes

ρ

Density of hydrogen peroxide solution

W


20

(H2O2 35% = 1.132; H2O2 50% = 1.195)

% by weight of hydrogen peroxide solution

Hydrogen peroxide

The following calculation formula are such that calculation can be done at every concentration of potassium permanganate solution and every concentration of hydrogen peroxide. Normally a 0.02 mol/l = 0.1 N potassium permanganate solution is applied.

Calculation of the H2O2-concentration in g/kg: g/kg H2O2 x − % =

x mol/l KMnO 4 ⋅ 5 ⋅ 34.0146 ⋅ V ⋅ 100 2 ⋅ M ⋅ W x mol/lKMnO 4 ⋅ 8503 .65 ⋅ V M ⋅ W

=

Example After impregnation a sample having a mass of 2.8 g is taken. For titration with 0.02mol/l KMnO4-solution (= 0,1 N) V = 8.5ml KMnO4-solution are consumed. How much H2O2 50% (W=50) in g/kg are on the fabric ? g/kg H2O2 50%ig =

0.02 ⋅ 8503.65 ⋅ 8.5 2.8 ⋅ 50

g/kg H2O2 50% = 10.3 g/kg

Calculation of H2O2-concentration in ml/kg: ml/lkg H2O2 x − % =

=

x mol/lKMnO4 ⋅ 5 ⋅ 34.0146 ⋅ V ⋅ 100 2 ⋅ M ⋅ W ⋅ ρ x mol/l KMnO 4 ⋅ 8503.65 ⋅ V M ⋅ W ⋅ ρ

Example After impregnation a samplehaving a mass of 2.8 g is taken. For titration with 0.02mol/l KMnO4-solution (= 0,1 N) V = 8,5ml KMnO 4solution is consumed. How much H2O2 50%(W=50) ml/kg are on the fabric ? ml/kg H2O 2 50%ig =

0.02 ⋅ 8503 .65 ⋅ 8.5 2.8 ⋅ 50 ⋅ 1.195

ml/kg H2O2 50% = 8.6 ml/kg

Reagents Potassium permanganate solution To produce the potassium permanganate solution preferably ready-made solutions are applied. If the solution is produced, it is done as follows: For a 0.02 mol/l KMnO4-solution 3.1607 g of solid potassium permanganate are weighted and dissolved in distilled water. After complete dissolution of the potassium permanganate, filling up with distilled water up to the marking in a 1 l graduated flask. èq=oK=_bfqifè=dj_e=

21

Hydrogen peroxide

Semi-quantitative determination of the hydrogen peroxide content with titanylchloride For hydrogen peroxide a semi quantitative determination can be done in a bath sample or directly on the fabric with titanylchloride. Particularly in case of cold dwelling procedures or steaming processes (before the washing off) the fabric can be determined very rapidly on its residual peroxide content and the recipe can be modified accordingly in case of need. Reaction of H2O2 with titanylchloride 2+

[Ti ⋅ aq]

+ H2O2 → [Ti(O2) ⋅ aq]2+ + H2O yellow to orange

The determination method is based on a colour change during the reaction of hydrogen peroxide with titanylchloride (TiOCl 2). Depending on the concentration of hydrogen peroxide there is a yellow to a deeply orange red dyeing. Depending on the determination of the hydrogen peroxide content on the fabric or in a solution, there are two colour scales at disposal.

Colour scale L

Determination in aqueous solutions – colour scale L

Determination of hydrogen peroxide in aqueous solutions.

0.5 ml of the test solution are mixed on a white droplet plate with 1 drop of titanylchloride solution. After approx. 1 min the colour shade is compared with the colour scale. The content of hydrogen peroxide is given in ml/l.

Colour scale T Determination of hydrogen peroxide directly on the fabric

Determination directly on the fabric – colour scale T 2 – 3 drops of titanylchloride solution are spotted onto the textile and the reagent is left to act for 20 – 30 s. The colour shade is compared with the colour scale. The content of hydrogen peroxide is given in ml/kg. If there is not any yellow colouration, there is hardly any hydrogen peroxide. Fabrication of the titanylchloride solution


22

10 ml of titan(IV)chloride is slowly dropped in 20 ml hydrochloric acid conc. and stirred. The reaction should be done under an extractor hood because of the very strong exothermic reaction and the development of hydrogen chloride (fumes). After having produced the mix, the solution is heated up to boiling and after 1 min 800 ml of diluted hydrochloric acid (1 part of conc. hydrochloric acid and two parts of water). After cooling off, the solution is ready for use.

Hydrogen peroxide


23

Hydrogen peroxide

Semi-quantitative determination of the hydrogen peroxide content with Merck-test sticks Application for aqueous solutions 1. 2. 3.

Take test sticks and close the tube again. Dip test stick for 1 sec into the test solution so that the reactive zone is completely wet. Take out test stick and shake off excess liquid and compare the reactive zone after 15 sec with the colour scale.

Depending on the blue dyeing of the stick, a value of 0 – 25 mg/l hydrogen peroxide is read off from the Mercktest stick container scale.


24

Alkali

Alkali In pretreatment the following alkali are used:

• • • •

Caustic soda (NaOH), solid or in solution Soda (sodium carbonate, Na 2CO3) Ammonia solution Silicates or silicate of soda

Determination of alkali content in liquors The quantitative determination of the three alkalis in the bath are carried out by acidimetrical titration with salt or sulphuric acid (mostly 0.1 N). The end point of the titration is indicated by a suitable acid-base indicator like e.g. phenol phthalein, methylorange or by a colour change.

Titration

Remark: In the annex there is a very much simplified version of the tiitration instruction.

Common indicators

An aliquot part, usually 1 to 10 ml, of the liquor is given into an Erlenmeyer flask containing some distilled water. It is titrated with the acid solution up to the colour change of the indicator.

Indicator

Phenol phthalein

Calculation

Colour change

of → to red → colourless

Methyl orange

orange → ret

Methyl red

yellow → ret

The parameter of calculation are the following:

V

Consumption in ml of acid-solution. Normally 0.1 mol/l (= 0.1 N) hydrochloric acid or 0.05 mol/l (= 0.1 N) sulphuric acid

F

ml of taken liquor quantity. Factor for the conversion on caustic soda, soda or ammonia

f

1 ml 1 ml 1 ml

= = =

4.0 mg caustic soda (NaOH) 5.3 mg soda (Na 2CO3) 1.7 mg ammoniac (NH 3)

Valid for hydrochloric acid of 0.1 mol/l (= 0,1 N) or sulphuric acid of 0.05 mol/l (= 0,1 N)e.


25

Alkali

Example F = 10 ml are taken of a bleaching liquor and titrated with hydrochloric acid of 0.1 mol/l with phenol phthalein as indicator. The consumption of the acid is: 11.2 ml. Which content of caustic soda (f = 4) in the liquor ? g/l NaOH100% =

For a 0.1 mol/l (= 0,1 N) hydrochloric acid or 0.05 mol/l (= 0,1 N) sulphuric acid, the concentrations of different alkalis are found as follows.

Alkali in g/l: g/l Alkali =

f ⋅ V F

4 ⋅ 11,2 10

g/l NaOH 100% = 4.5 g/l

Particularly in continuous processes caustic lye is applied instead of solid caustic soda. In such cases it is useful to get the caustic lye content in g/l or ml/l. It is necessary to take account of the density and the concentration of the applied caustic lye for the calculation. The parameters of calculation are the following:

Example For titration of F = 10ml of bleaching liquor of 0.1 mol/l of hydrochloric acid (= 0.1 N) V = 11.2 ml hydrochloric acid solution is used. How much caustic lye of 50% in g/l (W=50) does the bleaching liquor contain ? 4⋅11.2⋅100 g/l g/l NaOH50% = 10 ⋅ 50

V

Consumption in ml of acid solution. Usually hydrochloric acid of 0.1 mol/l (= 0,1 N) or sulphuric acid of 0.05 mol/l (= 0.1 N)

F

taken quantity of liquor in ml .

ρ

Density of caustic lye

W

% by weight of caustic lye

(NaOH 50%ig = 1.53)

Caustic lye in g/l:

NaOH 50% = 9 g/l

g/l NaOH x − % =

4 ⋅V ⋅100 F ⋅ W

Example For titration of F = 10ml bleaching liquor 0.1 mol/l hydrochloric acid (= 0.1 N) V = 11.2 ml hydrochloric acid solution is used. How much caustic of 50% lye in g/l (W=50, ρ=1.53) does the bleaching liquor contain ? ml/l NaOH 50 % =

4 ⋅11.2 ⋅100 10 ⋅ 50 ⋅1.53

ml/l NaOH 50%ig = 5,9 ml/l


26

Caustic lye in ml/l: ml/l NaOH x − % =

4 ⋅V ⋅100 F ⋅ W ⋅ ρ

Sodium hypochlorite (chlorine bleaching lye)

Sodium hypochlorite

(Chlorine

bleaching lye) Chemical formula: Molar mass:

NaOCl 74.5 g/mol

Properties of common chlorine bleaching lye Content of active chlorine of commercially available chlorine bleach

% by weight

12.5

g/l

approx. 150

„Active chlorine“ is the quantity of chlorine which is released during acidification of sodium hypochlorite with hydrochloric acid (see below)

Reactions of sodium hypochlorite The most important reactions for bleaching with sodium hypochlorite are the following: Hydrolysis

NaOCl + H2O → NaOH + HOCl

Release of bleaching agent

HOCl → HCl + [O]

Maximal HOCl-development

NaOCl + HCl → NaCl + HOCl

Formation of free chlorine „Active chlorine“

HOCl + HCl → H2O + Cl2

Summarized in a diagram the pH-dependance of the composition of sodium hypochlorite bleaching liquors is as follows: 100 HOCl

Cl 2 ] % [

OCl-

80

n 60 o i t a r t n e 40 c n o C

b e s t r a ng e f o r bleaching process

20

0 0

1

2

3

4

5

6 7 8 pH-value

9

10

11

12 13

The best pH range for bleaching is between 9 and 12.

14


27


Active chlorine Active chlorine HOCl + HCl → H2O + Cl2

Although chlorine does not have any bleaching effect, active chlorine is defined as the quantity of chlorine which is released during acidification of sodium hypochlorite with hydrochloric acid.

Determination of active chlorine content in sodium hypochlorite bleaching baths The quantitative determination of the content of active chlorine is done by a iodometric titration. Transformation of sodium hypochlorit e with iodide -

+

2 HOCl + 4 I + 2 H → 2 I2 + 2 Cl + 2 H2O Back titration of iodine with sodium thiosulphate 2-

-

2-

2 S2O3 + I2 → 2 I + S4O6

Out of an acid potassium iodide solution (KI) sodium hypochlorite separates an equivalent quantity of iodine (I) to the quantity of chlorine (Cl 2), and it can be titrated with sodium thiosulphate solution (Na 2S2O3). The equivalence mass ratios result of the reaction equation or the equivalence numbers of sodium thiosulphate and of chlorine (Cl 2 ). Equivalence Molar mass number z Chlorine

2

70.906 g/mol

Sodium thiosulphate

1

158.10 g/mol

The equivalence ratios are the following: n(eq) (Na 2 S 2 O3 ) = n(eq) (Cl 2 ) n (Na 2 S 2 O 3 ) ⋅ z (Na 2 S 2 O 3 ) = n (Cl 2 ) ⋅ z(Cl 2 ) = n (Na 2 S 2 O 3 ) =

m (Cl 2 ) ⋅ z (Cl 2 ) M (Cl 2 )

m (Cl 2 ) ⋅ z (Cl 2 ) M (Cl 2 ) ⋅ z (Na 2 S 2 O 3 )

Normally a 0.1 mol/l (= 0.1 N) Na 2 S 2 O3 -solution is applied. The calculation ist: m (Cl 2 ) ⋅ 2 0.1 mol Na 2 S 2 O 3 = 70.906 g/mol ⋅ 1 0.1 mol Na 2 S 2 O 3 ⋅ 70.906 g/mol ⋅ 1 2 m (Cl 2 ) = 3.545 g m (Cl 2 ) =

That means that 1 ml of a 0.1 mol/l (= 0,1 N) Na 2 S 2 O3 -solution corresponds to exactly 3.545 mg Cl 2 or active chlorine.


28


Procedure of Titration An aliquot part, usually 1 to 10ml, is taken from the bleaching liquor and given into an Erlenmeyer flask containing some distilled water and approx. 10ml potassium iodide solution (approx. of 10%). Then approx. 20ml of a sulphuric acid solution of 20% are added. The transformation which takes place of sodium hypochlorite with potassium iodide to iodine is recognisable by a stronger brown colouration of the solution. With a sodium thiosulphate solution of 0.1 ml/l (= 0.1 N) titration is done until a weak brown colouration is obtained. After addition of 5 ml of a starch solution (approx a solution of 1 % of some soluble starch) the titration solution gets a strong blue dyeing. Titration is continued with sodium thiosulphate solution until the titration solution becomes colourless.

Calculation The parameter of calculation are the following:

V

Consumption in ml of a Na 2S2O3-solution with a concentration of 0.1 mol/l (= 0.1 N).

F

ml of taken quantity of bleaching liquor

1ml of 0.1mol/l Na 2S2O3 = 0.00355g active chlorine

1ml 0.1mol/l Na2S2O3 = 0.00355g active chlorine

Example

Calculation of active chlorine content in g/l: g/l Active chlorine =

0.00355 ⋅ V ⋅ 1000 F

For titration of F = 10ml bleaching liquor with 0.1 mol/l (= 0.1 N) sodium thiosulphate solution are consumed V = 6,8 ml Na2S2O3 solution. How much active chlorine in g/l does the bleaching bath contain ? g/l Active chlorine =

0.00355 ⋅ 6.8 ⋅ 1 10

g/l Aktive chlorine = 2.41 g/l


29


Dechlorination Dechlorination has two purposes:

Formation of chloramines Protein compound

R-NH2

+

→ R-NHCl

NaOCl + NaOH

1.

Elimination of the active chlorine from the fabric, because it would damage the fibres during drying and storing.

2.

Separation of chloramines (chlorine protein compounds).

Vegetable fibres are composed of protein compounds of the protoplasma and form so-called chloramines in contact with chlorine bleach lye.

Chloramine

Chloramines tend to form hypochlorite in an humid atmosphere, and this has a fibre damaging effect during storing.

Decomposition of chloramines in a humid atmosphere

In addition to that chloramines separate hydrochloric acid during the drying process and this might cause fibre damage as well.

R-NHCl + H2O

Dechlorination agent Dechlorination can be done with reducing agents or with hydrogen peroxide: Dechlorination agent Sodium thiosulphate 24 HOCl + S 2O3 + H2O → 2+ 2 SO4 + 6 H + 4 Cl

Sodium thiosulphate (Antichlorine)

Sodium hydrogen sulphite HOCl + HSO3 → + HSO4 + H + Cl

Sodium hydrogen sulphite (Bisulphite)

Sodium dithionite 23 HOCl + S2O4 + H2O → 2+ 2 SO4 + 5 H + 3 Cl

Hydrogen peroxide HOCl + H2O2 → + Cl + H2O + H + O2


30

Sodium dithionite (Hydrosulphite)

Theoretically necessary quantity for the destruction of 1g/l of active chlorine 4 x HOCl = 2 x 35.5g active chlorine = 158.1g sodium thiosulphate

1g/l active chlorine = 0.55g/l sodium thiosulphate 1 x HOCl = ½ 35.5g active chlorine = 104.06g sodium hydrogen sulphite

1g/l active chlorine = 2.9g/l sodium hydrogene sulphite 3 x HOCl = 1.5 x 35.5g active chlorine = 158.1g sodium hydrogen sulphite

1g/l active chlorine = 1.5g/l sodium hydrogen sulphite 1 x HOCl = ½ 35.5g active chlorine = 34.02g hydrogen peroxide

Hydrogen peroxide

1g/l active chlorine = 0.48g/lH2O2 100% = 1.21ml/l H2O2 35% = 0.8ml/l H2O2 50%


Determination of active chlorine content commercially available chlorine bleach lyes

in

In commercially available chlorine bleaching lyes the active chlorine content usually is at 140 – 160 g/l. To test the content of active chlorine, the concentrated chlorine bleaching lye is diluted before the titration. Titration is done with the same method as for the diluted bleaching bath. A dilution of 20 – 50 ml concentrated chlorine bleach lye per liter with distilled water is advised.

Calculation The parameters of calculation are the following:

KV

Dilution of KV ml concentrated chlorine bleach lye per liter. Usually 20 – 50 ml/l.

V

Consumption in ml of Na 2S2O3- solution with a concentration of 0.1 mol/l (= 0.1 N).

F

ml of taken quantity of diluted chlorine bleach lye for titration. Example

Calculation of active chlorine content in g/l: g/l Active chlorine =

0.00355 ⋅ V ⋅ 1000 ⋅ 1000 F ⋅ KV

KV = 20 ml commercially available chlorine bleach lye was diluted on a liter. Of this diluted solution F = 10 ml were taken out and titrated with 0.1 mol/l (= 0.1 N) Na 2S2O3 solution. A consumption of V = 8.5 ml Na2S2O3 solution was found. How much active chlorine in g/l does the concentrated bleaching lye contain. g/l Active chlorine =

0.00355 ⋅ 8.5 ⋅1000 ⋅ 100 10 ⋅ 20

g/l Active chlorine = 150 g/l


31

Sodium chlorite

Sodium chlorite Chemical formula: Molar mass:

NaClO2 90.5 g/mol

Properties of commercially available sodium chlorite 30 vol.% solution

Sodium chlorite Short name NaClO2 concentrations

N 30 [g/kg]

approx. 245 (= 24.5 %)

[g/l]

300 slightly greenish-yellow clear liquid

Aspect Density (

20)

3

1 22

[g/cm ]

Solubility in water at 20 °C Start of crystallisation Reaction

unlimited approx. -15

[°C]

alkaline (pH-value approx.13)

Reactions of sodium chlorite The most important reactions for bleaching with sodium chlorite are the following. Alkaline sodium chlorite solutions are very stable at room temperature. In an acid medium, however, sodium chlorite solutions are rapidly decomposed. Hydrolysis

NaClO2 + H2O → NaOH + HClO2

Release of bleaching agent

HClO2 → HCl + 2 [O]

Decomposition of bleaching agent in an acid solution 5 HClO2

→ 4 ClO2 + HCl + 2 H2O

Formation of chlorine dioxide

3 HClO2 → 2 HClO3 + HCl èq=oK=_bfqifè=dj_e=

32

Sodium chlorite

Summarized in a diagram the pH dependance of the composition of sodium chlorite bleach liquors is as follows: 100 HClO2

ClO2-

80

] % [ n 60 o i t a r t n e 40 c n o C

ClO2 b e s t r a ng e f or bleaching process

20

0 0

1

2

3

4

5

6

7

8

9

10

11

12

pH-value

Determination of sodium chlorite content in bleach liquors The quantitative determination of the content of sodium chlorite content is obtained by iodometric titration.

Transformation of sodium chlorite with iodide -

Sodium chlorite separates from an acid potassium iodide solution (KI) a quantity of iodine (I) equivalent to the sodium chlorite (NaClO2), which can be titrated with sodium thiosulphate solution (Na 2S2O3).

-

Back titration of iodine with sodium thiosulphate 2-

The equivalence mass relations result from the reaction equation or equivalence numbers of sodium thiosulphate and sodium chlorite.

Equivalence number

Molar mass

Sodium chlorite

4

90.5 g/mol

Sodium thiosulphate

1

158.10 g/mol

+

ClO2 + 4 I + 4 H → 2 I2 + Cl + 2 H2O

-

2-

2 S2O3 + I2 → 2 I + S4O6


33

Sodium chlorite

The equivalence ratios result from: n(eq) (Na 2 S 2 O3 ) = n(eq) (NaClO 2 ) n (Na 2 S 2 O 3 ) ⋅ z (Na 2 S 2 O 3 ) = n (NaClO 2 ) ⋅ z(NaClO 2 ) = n (Na 2 S 2 O 3 ) =

m (NaClO 2 ) ⋅ z (NaClO 2 ) M (NaClO 2 )

m (NaClO 2 ) ⋅ z (NaClO 2 ) M (NaClO 2 ) ⋅ z (Na 2 S 2 O 3 )

Usually a solution of 0.1 mol/l (= 0.1 N) Na 2 S 2 O3 is applied. The following equation is valid: 0,1 mol Na 2 S 2 O 3 =

m (NaClO 2 ) ⋅ 4 90,5 g/mol ⋅ 1

0,1 mol Na 2 S 2 O 3 ⋅ 90,5 g/mol ⋅ 1 4 m (NaClO 2 ) = 2,2625 g m (NaClO 2 ) =

That means that 1 ml of a solution of 0.1 mol/l (= 0.1 N) Na 2 S 2 O3 - solution exactly corresponds to 0.00226g NaClO 2 100%.

Procedure of titration An aliquot part is taken, normally 1 to 10ml of the bleaching liquor and given into an Erlenmeyer flask containing some distilled water and approx. 10ml of potassium iodide solution (approx. 10%). Then approx. 20ml of a sulphuric acid solution of 20% are added. The transformation of sodium hypochlorite with potassium iodide to iodine becomes visible by a strong brown colouration of the solution. With a sodium thiosulphate solution of 0.1 ml/l (= 0.1 N) a titration is done until a slightly brown titration is obtained. After addition of 5 ml of a starch solution (approx. solution of 1 % of a soluble starch) the titration solution gets a strong blue colouration. Titration with a sodium thiosulphate solution is continued until the titration solution becomes colourless.


34

Sodium chlorite

Calculation The calculation parameters are the following:

V

Consumption in a Na 2S2O3- solution with a concentration of 0.1 mol/l (= 0.1 N).

F

Taken quantity of bleach liquor in ml

ρ

Density of sodium chlorite solution NaClO2 24.5% (30 Vol.%, N 30) = 1.22

W

% by weight of sodium chlorite solution

1ml of a 0.1mol/l Na 2S2O3 = 0.00226g NaClO 2 100 %

1ml 0.1mol/l Na2S2O3 = 0.00226g NaClO2 100 %

Calculation of sodium chlorite content in g/l: g/l NaClO 2 100% =

0.00226 ⋅ V ⋅ 1000 ⋅ 100 F ⋅ W

Usually sodium chlorite solutions are applied (mostly 24.5 % , 30 Vol.%, N 30).

Example For titration of F = 10ml of bleach liquor with 0.1 mol/l (= 0.1N) sodium thiosulphate solution V = 4.2ml Na2S2O3 solution is consumed. How much sodium chlorite 100% in g/l does the bleach liquor contain ? g/l NaClO 100% = 2

0,00226 ⋅ V ⋅ 1000 ⋅ 100 F ⋅ W ⋅ ρ

10 ⋅ 100

g/l NaClO2 100% = 0.95g/l

Example

Calculation of sodium chlorite content in ml/l:

ml/l NaClO2 100% =

0.00226 ⋅ 4.2 ⋅ 1000 ⋅ 100

For titration of F = 10ml of bleach liquor with 0.1 mol/l (= 0.1N) sodium hiosulphate solution V = 5.0ml Na2S2O3 solution is consumed. How much sodium chlorite 24.5% ml/l (W=24.5, ρ=1.22) does the bleach liquor contain ? ml/l NaClO

2

24,5% =

0.00226 ⋅ 5.0 ⋅ 1000 ⋅ 10 10 ⋅ 24.5 ⋅ 1.22

ml/l NaClO2 24.5% = 3.78ml/l


35

Sodium chlorite

Destruction of residual chlorite The destruction of residual chlorite is obtained in particular with the reducing agents sodium hydrogen sulphite (bisulphite) and sodiumsulphite. In contrast to the situation in sodium hypochlorite bleach, hydrogen peroxide and sodium thiosulphate are less suitable for this purpose. Before the reducing agents are added, the bleach liquor should be neutralized to avoid smell because of the formation of sulphure dioxide (SO 2) from the reducing agent.

Reducing agent Sodium hydrogen sulphite -

-

ClO2 + 2 HSO3 → + 2 SO4 + 2 H + Cl

Sodium hydrogen sulphite (Bisulphite)

-

2-


36

1 x 90.5g NaClO 2 = 2 x 104.06g NaHSO 3

1g/l NaClO2 100% = 2.3g/l sodium hydrogen sulphite 1 x 90.5g NaClO2 = 2 x 126.04g Na 2SO3 = 2 x 252.14g Na 2SO3 7 H2O

Sodium sulphite ClO2 + 2 SO3 → -2 SO4 + Cl

Theoretically necessary quantity to destruct 1g/l sodium chlorite 100%

Sodium sulphite

1g/l NaClO2 100% = 2.8g/l sodium sulphite = 5.6 g/l sodiumsulphite heptahydrate

Persulphates

Persulphates Properties of persulphates Name

Ammonium Potassium Sodium persulphate persulphate persulphate

Chemical formula

(NH4)2S2O8

K2S2O8

Na2S2O8

[g/mol]

228,2

270,3

238,2

[%]

6,9

5,8

6,5

10 °C

[g/100g]

49

3,0

46

20 °C

[g/100g]

54

5,5

54

30 °C

[g/100g]

59

8,8

58

Molar mass Active oxygen content (minimum) Solubility, g/100 g aqueous solution at

Persulphates slowly decompose particularly at higher temperatures.

in

aqueous

solution, Decomposition of persulphate 2-

For this reason solutions of persulphates are stable only to a limited degree. A higher bath temperature than 40 °C should be absolutely avoided.

S2O8 + H2O → 2 SO42- + 2 H+ + ½ O 2

Evidence of persulphate content in addition to hydrogen peroxide content in bleaching liquors In cold bleaches, persulphate is added in additon to hydrogen peroxide. On the contrary to hydrogen peroxide a direct titration of persulphate with potassium permanganate is not possible, because persulphates do practically not react with permanganate because of their rather high oxidation potential at room temperature. However the determination of the persulphate content is possible by an indirect titration . In the following the determination of hydrogen peroxide and persulphate in bleaching liquors will be described.


37

Persulphates

Principle of titration Titration of hydrogen peroxide and persulpate is done in the same bath sample as follows: 1.

A liquor sample is taken and first the content of hydrogen peroxide is titrated as usually with potassium permanganate. Because persulphate does not react with permanganate under these conditons, in this completely titrated sample there is only pure persulphate. Complete titration is absolutely necessary to destroy the hydrogen peroxide.

2.

A defined iron (II) salt solution is added to the completely titrated sample. A part of the iron (II) is oxidated by persulphate to iron(III). The iron(II) which was not oxidated is back titrated with potassium permanganate, and the content of persulphate is calculated.

Procedure 1. Fabrication of iron (II) (II) salt solution Ammonium iron(II)sulphate = Mohr’s salt

A suitable iron (II) salt for the titration of persulphates is the ammonium iron (II) sulphate, which is known under the name of Mohr’s salt.

(NH4)2Fe(SO4)2 ⋅ 6 H2O

Approx. 40 g of ammonium iron (II) sulphate are dissolved by vigourously shaking and with addition 100 ml of sulphuric acid 2+ of 10 % to one litre. The solution contains approx. 5.7 g/l Fe .

2. Determination of the content of iron (II) in the blank sample The content of iron (II) in the ammonium iron (II) sulphate solution (= blank sample) should be determined again before every titration.

The iron (II) of the fabricated ammonium iron (II) sulphate solution is slowly oxidated to iron (III) by oxygen from the air. For this reason the actual content of iron (II) has to be determined before the titration is done. 20 ml of the ammonium iron (II) sulphate solution are mixed with approx. 20 ml of sulphuric acid of 10 % and with a potassium permanganate solution (normally 0.02 mol/l = 0.1 N), which is applied for all further titrations, and tritrated until the colour shade change to light pink is obtained.


38

Persulphates

The consumption of potassium permanganate solution is recorded (VB). It serves for the calculation of the persulphate content.

VB = consumption of potassium permanganate solution in case of a titration of 20 ml ammonium iron II sulphate solution (= blank sample).

3. Determination of the content of hydrogen peroxide in the bleaching bath A liquor sample is taken, usually 5 – 10 ml with approx. 20 ml of sulphuric acid of 10 % and the content of hydrogen peroxide is determined with potassium permanganate (see also chapter HYDROGEN PEROXIDE).

Titration of hydrogen peroxide with a solution of 0.2 mol/l (= 0.1 N) KMnO4.

In cold bleaching liquors the content of hydrogen peroxide is normally rather high. For this reason it is advised to apply a KMnO 4 solution of 0.2 mol/l (= 1 N) instead of the usual 0.02 ml/l (= 0.1 N), so that the consumption is not too high. For the titration of persulpate a solution of KMnO 4 of 0.02 mol/l (= 0.1 N) should be applied. The completely titrated sample is applied for further titration.

4. Determination of the content of persulphate 20 ml of the ammonium iron (II) sulphate solution are added to the completely titrated sample. At any rate the same quantity of ammonium iron (II) sulphate solution has to be added as for the blank value determination .

VP = Consumption of potassium permanganate solution out of the titration of the before completely titrated liquor sample.

Then titration is done with the potassium permanganate solution which served for the determination of the content of iron (II) in the ammonium iron (II) sulphate solution (= blank sample), until the colour shade change to ligh pink is obtained (VP).


39

Persulphates

Calculation The parameters for the calculation are the following: F

ml taken quantity of bleaching liquor.

VB

Consumption of potassium permanganate solution with a concentration of x mol/l (usually 0.02 mol/l = 0.1 N) in titration of the ammonium iron (II) sulphate solution in the blank sample.

VP

Consumption of potassium permanganate solution with a concentration of x mol/l (usually 0.02mol/l = 0,1 N) in titration of completely titrated bath samples.

x mol/l KMnO4

Example

f

In a cold bleach bath the content of sodium persulphate is to be determined. Titration of 20 ml ammonium iron (II) sulphate solution (= blank vat) gave a consumption of 0.02 mol/l KMnO4- solution (= 0.1 N) of VB = 20.4 ml. F = 10 ml of the cold bleach bath was taken and first the content of hydrogen peroxide was determined with a solution of 0.2 mol/l (= 1 N) KMnO4 . The liquor sample which had been completely tritrated in this way was then mixed with 20 ml ammonium iron (II) sulphate solution and titrated with 0.02 mol/l KMnO4-solution (= 0.1 N) up to the colour shade change to light pink. A consumption of KMnO4 of VP = 13.7 ml was recorded. The content of sodium persulphate is calculated as follows: g/l Na - persulphat e =

1 ml 1 ml 1 ml

0.02 ⋅ 10


= = =

11.910 mg sodium persulphate 13.515 mg potassium persulphate 13.515 mg ammonium persulphate

for a solution of 0.02 mol/l of KMnO 4

Calculation of the H2O2-concentration: The determination and calculation of the hydrogen peroxide concentration is done as described in the chapter about HYDROGEN PEROXIDE.

Calculation of the persulphate concentration: The following calculation formula is such that it can be calculated with every concentration of potassium permanganate solution. Only the concentration in mol/l should be known. Independently from the applied potassium permanganate solution for the conversion on sodium-, potasium or ammonium persulphate the factors f have to be taken out of the above given table.

(20.4 - 13.7) ⋅ 0.02 ⋅ 11.

g/l Na-persulphate = 8 g/l

40

Concentration of the applied potassium permanganate solution. Normally 0.02 mol/l = 0.1 N Conversion factor for sodium-, potassium or ammonium persulphate.

g/l Persulphat e =

(VB - VP ) ⋅ xmol/lKMnO4 ⋅ f 0.02 ⋅ F

Silicates

Silicates Properties of commercially available sodium silicates Name

Sodium silicate

Sodium silicate

37/40

40/42

[g/cm ]

1,34 - 1,38

1,38 - 1,40

[°Be]

37 - 40

40 - 42

Silicium oxide SiO 2

[%]

26,5 - 28,5

28 - 30

Sodium oxide Na2O

[%]

8-9

8,5 - 9,3

Mole ratio (SiO2 : Na2O)

3,3 - 3,5

3,2 - 3,4

Weight ratio (SiO 2 : Na2O)

3,2 - 3,4

3,1 - 3,3

50 - 150

100 - 240

Density (ρ20) Density in °Be

Viscosity at 20°C

3

[mPa ⋅ s]

Properties of commercially available metasilicates Nametasilicate anhydrous

Name

Na-metasilicate Na-metasilicate 5-hydrate 9-hydrate

Na2SiO3

Na2SiO3⋅5 H2O

Na2SiO3⋅9 H2O

[g/mol]

140

230

302

Silicium oxide SiO2

[%]

46.2 - 47.6

28.0 - 29.4

21.8 - 23.8

Sodium oxide Na2O

[%]

50.4 - 51.8

28.1 - 29.5

21.7 - 23.7

Dry substance

[%]

96.5 - 99.5

56.5 - 58.5

44 - 47

Chemical formula Molar mass

Other properties of silicate of soda • •

In combination with magnesium compounds (e.g. Epsom salt) there is a good stabilizing effect in the hydrogen peroxide bleach. Silicates increase the soil suspending property of washing baths.


41

Hardness of water

Silicate precipitations with hardening substances (schematically) Ca ONa O

O

Mg O

ONa

OH

O

Si O

Si O

Si O

Si O

Si O

Si O

Si O

Si O

O

OH

O

O

ONa

O

ONa

Ca

•

Mg

ONa

O

OH

ONa

ONa

OH

O

ONa

Si O

Si O

Si O

Si O

Si O

Si O

Si O

Si O

OH

O

O

ONa

O

O

O

O

Mg

•

O

OH

Ca

O

ONa

•

Ca

•

Silicates have a very high sequestering power on heavy metals and thus have an anticatalytic effect Silicates hydrolyze at high temperatures and can form insoluble silicic acid. Silicates form insoluble compounds with alkaline earths and can cause sediments on fibres and machine parts. Silicates have a high buffering power.

Mg

Ca-silicate deposits on cotton fibres

Alkali content of silicates For the calculation of the alkali content (caustic lye) of silicates the following decomposition reaction is taken as a basis: Na2O

+

H2O

→

2 NaOH

61.979 g/mol

+

18.0152 g/mol

→

2 ⋅ 39.99 g/mol

2 ⋅ 39.99 g = 79.98 g of sodium hydroxide (NaOH) are formed of 61.979g Na2O. The parameter of calculation are the following: Remark The data of density and content of sodium oxide are the average values of above given tables. It is possible that the values differ from the applied sodium silicate. Therefore the data should better be taken from the specifications.

Example How much NaOH g.kg does sodium silicate 37/40 contain? The Na2O-content of this silicate of soda is indicated with 8-9 % in the table (medium value 8.5 %). NaOH 100% = 12.904 · 8.5 = 110g/kg = 11 %


42

W

ρ V

Content of sodium oxide (Na2O) (37/40 = 8.5%; 40/42 = 8.9%)

Density of sodium silicate (37/40 = 1.36; 40/42 = 1.39)

Applied quantity of silicate of soda in ml/l (in case of metasilicates in g/l)

Calculation of NaOH-concentration in g/kg: Corresponding to the sodium oxide indications (Na2O) of above given table the sodium hydroxide content of the silicates can be calculated as follows. 79,98 ⋅ 10 NaOH 100% [g/kg ] = ⋅W 61.979

= 12.904 ⋅ W

Silicates

Calculation of NaOH-concentration in g/l: In bleach liquors sodium silicate is normally applied in ml/l. The sodium hydroxide content (NaOH) out of sodium of silicate in such a bleaching bath is calculated as follows: NaOH 100% [g/l ] =

79.98 ⋅ W ⋅ V ⋅ ρ 61.979 ⋅ 1000

Example In a bleach liquor V=10ml sodium silicate 37/40 (ρ=1.36, W=8.5) is applied. How much NaOH 100 % in g/l does the bath contain ? NaOH 100% [g/l ] =

=

12.904 ⋅ W ⋅ V ⋅ ρ 1000

12,904 ⋅ 8,5 ⋅10 ⋅ 1,36 1000

NaOH 100% = 1.49 g/l

For metasilicates it is not possible to indicate density because it is a solid substance. Therefore the calculation formula for metasilicates is the follwing: NaOH 100% [g/l ] =

79.98 ⋅ W ⋅ V 61.979 ⋅ 1000

=

12.904 ⋅ W ⋅ V 1000


43

Hardness of water

Hardness of water Hardness classification Total hardness °dH

Description

0-7 7-14 14-21 > 21

soft medium hard very hard

Total hardness (GH) Total concentration of all dissolved calciumand magnesium ions. Carbonate hardness (KH) = Cand Mg-hydrogen carbonates. During boiling insoluble Ca- or Mg-carbonate is formed: Ca(HCO3)2 → CaCO3 + H2O + CO2

Permanent hardness = Caand Mg-chlorides, sulphates, nitrate and others

Hardness of industrial waters can have a considerable influence on pretreatment and dyeing results. High hardness for example can cause:

• •

Deposits of hardening substances on machines or textiles. Precipitations of dyes which are sensitive to hardness in the dyeing liquor.

For this reason a regular control of the hardness of the industrial water can be very helpful so that possible reasons for defects can be recognized early and eliminated. On thebasis of the total hardness of water it is differentiated between carbonate hardness (former temporary hardness) and permanent hardness. The carbonate hardness forms insoluble Ca- or Mg-carbonates during boiling and therefore causes deposits whereas the permanent hardness remains in solution even at a higher temperature.

Determination of water hardness (total hardness) Ca- and Mg-ions can be determined in ammoniacal solution complexometrically with EDTA (ethylene diamine tetraacetate) and with Eriochrom black T (or indicator buffer tablet) as indicator.

Procedure of titration

100 ml are taken of the water sample and an indicator-buffer tablet is dissolved in it. 2 ml ammonia 25 % are added and heated up at 40 °C. The solution becomes more or le ss red depending on the water hardness. Then titration is carried out immediately with 0.1 mol/l EDTA-solution from red to green. Calculation

The parameters of calculation are the following:


44

V

Consumption in ml of EDTA-solution at a concentration of x mol/l.

F

Taken quantity of water sample in ml

x mol/l EDTA

Concentration of applied EDTA-solution, usually 0.01 mol/l.

Hardness of water

EDTA always forms with metal ions a 1:1 complex. 1 mol EDTA binds 1 mol of a metal ion, e.g. calcium.

EDTA-complex O

O

1 ml of 0.01 mol/l EDTA-solution

= 0.4008 mg = 0.5608 mg = 1.00 mg

0.01 mmol metal

= 0.24305 mg Mg = 0.4030 mg MgO = 0.8431 mg MgCO3

x mol/l EDTA ⋅ V ⋅1000 F

With this formula the content of CaCO3 can be exactly calculated in mg/l.

Calculation of content of hardening substances in °dH: According to definition:

1 °dH = 10 mg/l CaO

= 7.19 mg/l MgO

CH2

N O

CH2 O

CH2 CH2

C O

Example For the titration of F = 100ml of a water sample with 0.01 mol/l EDTA-solution V = 13ml EDTAsolution is consumed. How much mmol/l of hardness does water contain ? mmol/l =

0.01mol/l EDTA ⋅ 13 ⋅ 1000 100

mmol/l hardness = 1.3 mmol/l

Example For the titration of F = 100ml of a water sample 0.01 mol/l EDTA-solution V = 13ml EDTAsolution is consumed. How much °dH has the water ? °dH =

x mol/l EDTA ⋅ V ⋅ 5.608 ⋅ 1000 F

N Ca2+

C

CH2

CH2

O

O

Calculation of content of hardening substances in mmol/l: mmol/l =

C

Ca CaO CaCO3

corresponds to

°dH =

C

O

Table:

0,01mol/l EDTA ⋅13 ⋅ 5.608 ⋅ 1000 100

°dH = 7.3 °dH


45

Hardness of water

Conversion factors for common units of water hardness

Definition of different hardness data 1°

German hardness

10 mg/l CaO

1°

French hardness

10 mg/l CaCO3

1°

English hardness

1

American hardness (USA)

10 mg/0,7 l CaCO3

1

1°

English hardness

French hardness

German hardness

Russian hardness

ppm as CaCO3

1

7,02

10

5,6

40

100

0,14

1

1,429

0,7999

5,714

14,29

0,1

0,7

1

0,5599

4

10

1°

German hardness

0,18

1,25

1,786

1

7,144

17,85

1°

Russian hardness

0,025

0,175

0,25

0,14

1

2,5

0,01

0,07

0,1

0,06

0,4

1

1 mg/l CaCO3

1

46

English hardness

1 ° French hardness

14.29 mg/l CaCO4


mmol/l alkaline earth ions

mmol/l Alkaline earth ions

ppm as CaCO3

Average polymerisation degree and fluidity

Average degree of polymerisation (DP-value) The cellulose molecule is a polysaccharide composed of β-1.4 linked glucose units. The so-called polymerisation degree gives evidence of the number of chain elements (glucose units). E.g. if there is chemical damage in bleaching, the long chain molecule is separated into smaller fragments. The polymerisation degree decreases. If the cellulose is completely dissolved in a solvent, the viscosity of the solution is higher at a higher polymerisation degree, because there are more of the bigger molecules and vice versa. Due to this the polymerisation degree of a cellulose fibre can be determined by a viscosity measurement.

CH2OH O

OH O

OH

OH O

OH

CH2OH O O

CH2OH

OH OH

n/3

n = degree of polymerisation

The average polymerisation degree only reflects the extent of a chemical damage, and can be used to distinguish between chemical and mechanic damage. This is different from the determination of the tear strength e.g. , the average polymerisation degree is completely independent from the structure of the fabric and thus much more specific.

Measuring method There are four procedures for the viscosimetric determination of the polymerisation degree of cellulose fibres and cellulose material with the difference in solvents.

• • • •

Cuoxam procedure The cupriethylene diamine procedure EWNN - procedure Nitrate procedure

The fibre material is dissolved in a solvent according to all procedures (in case of the nitrate procedure after a preceding nitration) and the running time of the solution is measured by means of a capillary as well as the running time of the pure solvent as reference. The fibre material applied for the DP value determination should be free of sizes, finishs etc.

Remark Difficulties can be caused by resin finished, reactive dyed or mercerized fabrics depending on the procedure because sometimes the fibre material is not completely dissoved in the solvent and measuring becomes impossible.

The methods for the determination of the average polymerisation degree are all very difficult, and a lot of experience and accuracy is needed, so that the measurements should be carried out only in well equipped laboratories. èq=oK=_bfqifè=dj_e=

47


Calculations DP-values of different fibres Substrate

DP - value

Natural fibres: Cotton, flax, Ramie

2000 – 3000

Regenerated cellulose: Copper procedure Viscose procedure Acetate procedure

400 – 500 250 – 400 200 – 300

According to Staudinger the following formula is valid for the DP-value: DP =

η − η0 η

η: η0: c: Km:

⋅

1 1 ⋅ C km

Runnning time of solution in sec. Running time of solvent in sec Cellulose concentration in g/l Constant of solvent

There is a decrease of the polymerisation degree in case of every damage, and its amount on the other hand gives conclusion on degree of the damage. According to O. Eisenhut the functioning of polymerisation degree - decrease = fibre damage is defined as damage factor by the following formula: æ 2000 2000 ö log ç − + 1÷ Pt è Ptx ø s = log 2 Pt: DP – value of cellulose before the chemical treatment Ptx: DP – value of cellulose after the chemical treatment 2000: DP – value of CO as point of reference

The relation of the DP value before and after the damaging and the damaging factor is shown in the following graph. Judgment of damaging degree s-factor 0.01–0.20 0.21–0.30 0.31–0.50 0.51–0.75 > 0.75

damaging factor

judgment very good – undamaged good, very gentle bleaching sufficient slightly damaged very much damaged

3600 g n i g a m a d e r o f e b e u l a v P D

1,2

1,0

0,8

0,6

0,4

48

0,0

3200 2800 2400 2000 1600 800

1200

1600

2000

2400

DP-value after damaging


0,2

2800

3200

3600


Fluidity F In different countries not the DP-value but the fluidity number is given. The basis of the measuring procedure to determine the fluidity number is like the principle of the DP-determination, that means the determination of viscosities. Strictly speaking the fluidity is the reciprocal value of the dynamic viscosity.

Judgement of fluidity Fluidity

Calculations

≤2

The fluidity formula is:

3.6-5.0 5.1-8.0 > 8.0

2.1-3.5

F=

C' t −

C: k: t: ρ:

C' =

k t

Judgement undamaged good, very gentle bleach sufficient slightly damaged very damaged

C ρ

Constant of viscosimeter Factor of correction Run-out time of solvent Density of solvent

There is the following relation between DP-value and fluidity: æ 74,35 + F ö DP = 2032 ⋅ ç log ÷ − 573 F è ø

Illustrated in a diagram: Relation between DP value and fluidity 3400 3000 2600 e u 2200 l a v P 1800 D

1400 1000 600 0

2

4

6

8

10

12

14

16

18

20

Fluidity


49

Annex – Density and concentration of sulphuric acid, hydrochloric acid, nitric acid, caustic lye and caustic potash

Annex Density and concentration of sulphuric acid, hydrochloric acid, nitric acid, caustic lye and caustic potash solution Density

°Be

ρ20

Sulphuric acid

Nitric acid

Caustic lye

Caustic potash

% w/w

g/l

% w/w

g/l

% w/w

g/l

% w/w

g/l

% w/w

g/l

1,000

0,0

0,261

2,609

0,360

3,600

0,333

3,330

0,159

1,590

0,197

1,970

1,005

0,7

0,985

9,904

1,360

13,670

1,255

12,610

0,602

6,050

0,743

7,470

1,010

1,4

1,731

17,483

2,360

23,840

2,164

21,860

1,045

10,550

1,295

13,080

1,015

2,1

2,485

25,223

3,370

34,210

3,073

31,190

1,490

15,120

1,839

18,670

1,020

2,7

3,242

33,068

4,390

44,780

3,982

40,620

1,937

19,760

2,380

24,280

1,025

3,4

4,000

41,000

5,410

55,450

4,883

50,050

2,384

24,440

2,931

30,040

1,030

4,1

4,746

48,884

6,430

66,230

5,783

59,570

2,839

29,240

3,480

35,840

1,035

4,7

5,493

56,852

7,460

77,210

6,661

68,940

3,289

34,040

4,030

41,710

1,040

5,4

6,237

64,865

8,490

88,300

7,530

78,310

3,735

38,840

4,580

47,630

1,045

6,0

6,956

72,690

9,510

99,380

8,398

87,760

4,199

43,880

5,121

53,510

1,050

6,7

7,704

80,892

10,520

110,460

9,259

97,220

4,655

48,880

5,660

59,430

1,055

7,4

8,415

88,778

11,520

121,540

10,120

106,770

5,107

53,880

6,200

65,410

1,060

8,0

9,129

96,767

12,510

132,610

10,970

116,280

5,562

58,960

6,740

71,440

1,065

8,7

9,843

104,828

13,500

143,780

11,810

125,780

6,017

64,080

7,280

77,530

1,070

9,4

10,510

112,460

14,490

155,040

12,650

135,360

6,471

69,240

7,820

83,670

1,075

10,0

11,260

121,040

15,480

166,410

13,480

144,910

6,928

74,480

8,360

89,870

1,080

10,6

11,960

129,170

16,470

177,880

14,310

154,550

7,378

79,680

8,890

96,010

1,085

11,2

12,660

137,360

17,450

189,330

15,130

164,160

7,827

84,920

9,429

102,310

1,090

11,9

13,360

145,620

18,430

200,890

15,950

173,860

8,283

90,280

9,960

108,560

1,095

12,4

14,040

153,740

19,410

212,540

16,760

183,520

8,734

95,640

10,489

114,860

1,100

13,0

14,730

162,030

20,390

224,290

17,580

193,380

9,189

101,080

11,030

121,330

1,105

13,6

15,410

170,280

21,360

236,030

18,390

203,210

9,643

106,560

11,560

127,740

1,110

14,2

16,080

178,490

22,330

247,860

19,190

213,010

10,097

112,080

12,080

134,090

1,115

19,3

16,760

186,870

23,290

259,680

20,000

223,000

10,554

117,680

12,610

140,600

1,120

15,4

17,430

195,220

24,250

271,600

20,790

232,850

11,007

123,280

13,140

147,170

1,125

16,0

18,090

203,510

25,220

283,720

21,590

242,890

11,463

128,960

13,660

153,670

1,130

16,5

18,760

211,990

26,200

296,060

22,380

252,890

11,919

134,680

14,190

160,350

1,135

17,1

19,420

220,420

27,180

308,490

23,160

262,870

12,344

140,100

14,706

166,910

1,140

17,7

20,080

228,910

28,180

321,250

23,940

272,920

12,825

146,200

15,220

173,510

1,145

18,3

20,730

237,360

29,170

334,000

24,710

282,930

13,279

152,040

15,741

180,230

1,150

18,8

21,380

245,870

30,140

346,610

25,480

293,020

13,729

157,880

16,260

186,990


50

Hydochloric acid

Annex – Density and concentration of sulphuric acid, hydrochloric acid, nitric acid, caustic lye and caustic potas

Density

°Be

ρ20

Sulphuric acid Hydrochloric aici

Nitric acid

Caustic lye

% w/w

g/l

% w/w

g/l

% w/w

g/l

% w/w

g/l

Caustic potash % w/w

g/l

1,155

19,3

22,030

254,450

31,140

359,670

26,240

303,070

14,182

163,800

16,780

193,810

1,160

19,8

22,670

262,970

32,140

372,820

27,000

313,200

14,634

169,760

17,290

200,560

1,165

20,3

23,309

271,550

33,161

386,320

27,761

323,410

15,090

175,800

17,810

207,490

1,170

20,9

23,950

280,210

34,180

399,910

28,510

333,570

15,538

181,800

18,320

214,340

1,175

21,4

24,580

288,810

35,200

413,600

29,250

343,690

15,990

187,880

18,840

221,370

1,180

22,0

25,210

297,480

36,230

427,510

30,000

354,000

16,441

194,000

19,350

228,330

1,185

22,5

25,840

306,200

37,270

441,650

30,740

364,270

16,891

200,160

19,860

235,340

1,190

23,1

26,470

314,990

38,320

456,010

31,470

374,490

17,345

206,400

20,370

242,400

1,195

23,5

27,100

323,850

39,370

470,470

32,210

384,910

17,797

212,680

20,879

249,510

1,200

24,0

27,720

332,640

-

32,948

395,380

18,253

219,040

21,380

256,560

1,205

24,5

28,330

341,380

-

33,680

405,840

18,709

225,440

21,880

263,650

1,210

25,0

28,950

350,290

-

34,410

416,360

19,160

231,840

22,380

270,800

1,215

25,5

29,570

359,280

-

35,160

427,200

19,615

238,320

22,880

277,990

1,220

26,0

30,180

368,200

-

35,930

438,350

20,072

244,880

23,380

285,240

1,225

26,4

30,790

377,180

-

36,700

449,580

20,526

251,440

23,869

292,400

1,230

26,9

31,400

386,220

-

37,480

461,000

20,979

258,040

24,370

299,750

1,235

27,4

32,010

395,320

-

38,250

472,390

21,438

264,760

24,860

307,020

1,240

27,9

32,610

404,360

-

39,020

483,850

21,897

271,520

25,360

314,460

1,245

28,4

33,220

413,590

-

39,800

495,510

22,355

278,320

25,850

321,830

1,250

28,8

33,820

422,750

-

40,580

507,250

22,813

285,160

26,340

329,250

1,255

29,3

34,420

431,970

-

41,360

519,070

23,273

292,080

26,830

336,720

1,260

29,7

35,010

441,130

-

42,140

530,960

23,730

299,000

27,320

344,230

1,265

30,2

35,600

450,340

-

42,920

542,940

24,190

306,000

27,800

351,670

1,270

3,6

36,190

459,610

-

43,700

554,990

24,643

312,960

28,290

359,280

1,275

31,1

36,780

468,940

-

44,480

567,120

25,098

320,000

28,770

366,820

1,280

31,5

37,360

478,210

-

45,270

579,460

25,556

327,120

29,250

374,400

1,285

32,0

37,950

487,660

-

46,060

591,870

26,014

334,280

29,731

382,040

1,290

32,4

38,530

497,040

-

46,850

604,370

26,478

341,560

30,210

389,710

1,295

32,8

39,100

506,340

-

47,630

616,810

26,941

348,880

30,680

397,300

1,300

33,3

39,680

515,840

-

48,420

629,460

27,403

356,240

31,150

404,950


51


Density

°Be

ρ20

Sulphuric acid Hydrochloric acid % w/w

g/l

Caustic lye

Caustic potash

g/l

% w/w

g/l

% w/w

g/l

% w/w

g/l

1,305

33,7

40,250

525,260

-

49,210

642,190

27,868

363,680

31,620

412,640

1,310

34,2

40,820

534,740

-

50,000

655,000

28,330

371,120

32,090

420,380

1,315

34,6

41,390

544,280

-

50,850

668,680

28,794

378,640

32,560

428,170

1,320

35,0

41,950

553,740

-

51,710

682,570

29,261

386,240

33,030

436,000

1,325

35,4

42,510

563,260

-

52,560

696,420

29,727

393,880

33,500

443,880

1,330

35,8

43,070

572,830

-

53,410

710,350

30,195

401,600

33,970

451,800

1,335

36,2

43,620

582,330

-

54,270

724,500

30,652

409,200

34,430

459,640

1,340

36,6

44,170

591,880

-

55,130

738,740

31,134

417,200

34,900

467,660

1,345

37,0

44,720

601,480

-

56,040

753,740

31,613

425,200

35,360

475,590

1,350

37,4

45,260

611,010

-

56,950

768,830

32,089

433,200

35,820

483,570

1,355

37,8

45,800

620,590

-

57,870

784,140

32,561

441,200

36,280

491,590

1,360

38,2

46,330

630,090

-

58,780

799,410

33,059

449,600

36,735

499,600

1,365

38,6

46,860

639,640

-

59,689

814,760

33,553

458,000

37,190

507,640

1,370

39,0

47,390

649,240

-

60,670

831,180

34,015

466,000

37,650

515,810

1,375

39,4

47,920

658,900

-

61,689

848,230

34,502

474,400

38,105

523,950

1,380

39,8

48,450

668,610

-

62,700

865,260

35,014

483,200

38,560

532,130

1,385

40,1

48,970

678,230

-

63,721

882,530

35,495

491,600

39,010

540,290

1,390

40,5

49,480

687,770

-

64,740

899,890

36,000

500,400

39,460

548,490

1,395

40,8

49,990

697,360

-

65,840

918,470

36,502

509,200

39,920

556,890

1,400

41,2

50,500

707,000

-

66,970

937,580

37,000

518,000

40,370

565,180

1,405

41,6

50,967

716,090

-

68,100

956,810

37,495

526,800

40,820

573,520

1,410

42,0

51,520

726,430

-

69,230

976,140

37,986

535,600

41,260

581,770

1,415

42,3

51,984

735,580

-

70,390

996,020

38,473

544,400

41,710

590,200

1,420

42,7

52,510

745,640

-

71,630

1017,150

38,986

553,600

42,155

598,600

1,425

43,1

53,010

755,390

-

72,860

1038,250

39,495

562,800

42,600

607,050

1,430

43,4

53,500

765,050

-

74,090

1059,490

40,000

572,000

43,040

615,470

1,435

43,8

54,000

774,900

-

75,351

1081,280

40,502

581,200

43,479

623,930

1,440

44,1

54,490

784,660

-

76,710

1104,620

41,028

590,800

43,920

632,450

1,445

44,4

54,970

794,320

-

78,070

1128,110

41,550

600,400

44,360

641,000

1,450

44,8

55,450

804,030

-

79,430

1151,740

42,069

610,000

44,790

649,460


52

% w/w

Nitric acid


Density

°Be

ρ20


g/l

% w/w

Nitric acid

Caustic lye

Caustic potash

g/l

% w/w

g/l

% w/w

g/l

% w/w

g/l

1,455

45,1

55,930

813,780

-

80,880

1176,800

42,584

619,600

45,230

658,100

1,460

45,4

56,410

823,590

-

82,390

1202,890

43,123

629,600

45,660

666,640

1,465

45,8

56,890

833,440

-

83,911

1229,290

43,631

639,200

46,094

675,280

1,470

46,1

57,377

843,440

-

85,500

1256,850

44,163

649,200

43,469

638,990

1,475

46,4

57,840

853,140

-

87,289

1287,520

44,692

659,200

46,960

692,660

1,480

46,8

58,310

862,990

-

89,070

1318,240

45,216

669,200

47,390

701,370

1,485

47,1

58,780

872,880

-

91,130

1353,280

45,737

679,200

47,820

710,130

1,490

47,4

59,240

882,680

-

93,490

1393,000

46,255

689,200

48,250

718,930

1,495

47,8

59,700

892,520

-

95,460

1427,120

46,796

699,600

48,674

727,680

1,500

48,1

60,170

902,550

-

96,730

1450,950

47,333

710,000

49,100

736,500

1,505

48,4

60,620

912,330

-

97,990

1474,750

47,841

720,000

49,530

745,430

1,510

48,7

61,080

922,310

-

99,260

1498,830

48,371

730,400

49,950

754,250

1,515

49,0

61,540

932,330

-

-

48,898

740,800

50,380

763,260

1,520

49,4

62,000

942,400

-

-

49,421

751,200

50,800

772,160

1,525

49,7

62,450

952,360

-

-

49,967

762,000

51,220

781,100

1,530

50,0

62,910

962,520

-

-

50,484

772,400

51,640

790,090

1,535

50,3

63,360

972,580

-

-

-

-

1,540

50,6

63,810

982,670

-

-

-

-

1,545

50,9

64,260

992,810

-

-

-

-

1,550

51,2

64,710

1003,010

-

-

-

-

1,555

51,5

65,150

1013,090

-

-

-

-

1,560

51,8

65,590

1023,200

-

-

-

-

1,565

52,1

66,030

1033,370

-

-

-

-

1,570

52,4

66,470

1043,580

-

-

-

-

1,575

52,7

66,910

1053,840

-

-

-

-

1,580

53,0

67,350

1064,130

-

-

-

-

1,585

53,3

67,790

1074,470

-

-

-

-

1,590

53,6

68,230

1084,860

-

-

-

-

1,595

53,9

68,660

1095,120

-

-

-

-

1,600

54,1

69,090

1105,440

-

-

-

-


53


Density

°Be

ρ20


g/l

g/l

% w/w

g/l

Caustic lye % w/w

g/l


g/l

1,605

54,4

69,530

1115,960

-

-

-

-

1,610

54,7

69,960

1126,360

-

-

-

-

1,615

55,0

70,390

1136,800

-

-

-

-

1,620

55,2

70,820

1147,280

-

-

-

-

1,625

55,5

71,250

1157,810

-

-

-

-

1,630

55,8

71,670

1168,220

-

-

-

-

1,635

56,0

72,090

1178,670

-

-

-

-

1,640

56,3

72,520

1189,330

-

-

-

-

1,645

56,6

72,950

1200,030

-

-

-

-

1,650

56,9

73,370

1210,610

-

-

-

-

1,655

57,9

73,800

1221,390

-

-

-

-

1,660

57,1

74,220

1232,050

-

-

-

-

1,665

57,4

74,640

1242,750

-

-

-

-

1,670

57,7

75,070

1253,670

-

-

-

-

1,675

58,2

75,490

1264,450

-

-

-

-

1,680

58,4

75,920

1275,460

-

-

-

-

1,685

58,7

76,340

1286,330

-

-

-

-

1,690

58,9

76,770

1297,410

-

-

-

-

1,695

59,2

77,200

1308,540

-

-

-

-

1,700

59,5

77,630

1319,710

-

-

-

-

1,705

59,7

78,060

1330,920

-

-

-

-

1,710

60,0

78,490

1342,180

-

-

-

-

1,715

60,2

78,930

1353,650

-

-

-

-

1,720

60,4

79,370

1365,160

-

-

-

-

1,725

60,6

79,810

1376,720

-

-

-

-

1,730

60,9

80,250

1388,330

-

-

-

-

1,735

61,1

80,700

1400,150

-

-

-

-

1,740

61,4

81,160

1412,180

-

-

-

-

1,745

61,6

81,620

1424,270

-

-

-

-

1,750

61,8

82,090

1436,580

-

-

-

-


54

% w/w

Nitric acid


Density

°Be

ρ20


g/l

% w/w

g/l

Nitric acid % w/w

g/l

Caustic lye % w/w

g/l


g/l

1,755

62,1

82,570

1449,110

-

-

-

-

1,760

62,3

83,060

1461,860

-

-

-

-

1,765

62,5

83,576

1475,110

-

-

-

-

1,770

62,8

84,080

1488,220

-

-

-

-

1,775

63,0

84,610

1501,830

-

-

-

-

1,780

63,2

85,160

1515,850

-

-

-

-

1,785

63,5

85,740

1530,460

-

-

-

-

1,790

63,7

86,350

1545,670

-

-

-

-

1,795

64,0

86,990

1561,470

-

-

-

-

1,800

64,2

87,690

1578,420

-

-

-

-

1,805

64,4

88,430

1596,160

-

-

-

-

1,810

64,6

89,230

1615,060

-

-

-

-

1,815

64,8

90,120

1635,680

-

-

-

-

1,820

65,0

91,110

1658,200

-

-

-

-

1,821

65,0

91,334

1663,190

-

-

-

-

1,822

65,1

91,560

1668,220

-

-

-

-

1,823

65,1

91,780

1673,150

-

-

-

-

1,824

65,2

92,000

1678,080

-

-

-

-

1,825

65,2

92,250

1683,560

-

-

-

-

1,826

65,3

92,510

1689,230

-

-

-

-

1,827

65,3

92,825

1695,910

-

-

-

-

1,828

65,4

93,030

1700,590

-

-

-

-

1,829

65,4

93,361

1707,570

-

-

-

-

1,830

65,4

93,640

1713,610

-

-

-

-

1,840

65,9

95,598

1759,000

-

-

-

-


55

Annex – Brief instruction Titration of hydrogen peroxide

Brief instruction - Titration of hydrogen peroxide Procedure of titration Remark Calculation is only valid for a 0.02 mol/l (= 0.1N) potassium permanganate solution.

An aliquot part is taken out, usually 1 to 10 ml, of the bleaching bath and given into an Erlenmeyer flask containing approx. 10 ml of a sulphuric acid of 20%. Titration is done immediately with a potassium permanganate solution of 0.02 mol/l (= 0./1 N) on a first persisting pink-violet colouration.

Calculation Valid for a potassium permanganate solution of 0.02 mol/l (= 0.1 N) Factor for

Example For titration of 2 ml bleach liquor with solution of 0.02mol/l KMnO4 (= 0.1 N) 8.7ml of KMnO4-solution are consumed. How much H2O2 of 50% in ml/l does the bleaching liquor contain ? The factor for 2 ml of bleaching liquor and of H2O2 50% is 1.423 (see table). ml/l H2O2 50% = 8.7 · 1.423 = 12.4 ml/l


56

Sample of H2O2 100% bleach liquor in g/l

Factor for

Factor for

H2O2 50%

H2O2 35%

in g/l

in ml/l

in g/l

in ml/l

1 ml

1,701

3,401

2,846

4,859

4,293

2 ml

0,850

1,701

1,423

2,430

2,146

5 ml

0,340

0,680

0,569

0,972

0,859

10 ml

0,170

0,340

0,285

0,486

0,429

ml/l H2O2 x-% = consumption of KMnO 4-solution ·factor

Annex – Brief instruction Titration of caustic lye

Brief instruction - Titration of caustic soda Procedure of titration

Remark

An aliquot part, usually 1 to 10 ml of the bath are taken and given into an Erlenmeyer flask containing some distilled water. Titration is done with 0.1 mol/l hydrochloric acid or 0.05 mol/l sulphuric acid (both of 0.1 N) up to the colour shade change of the indicator phenol phthaleine of red to colourless.

The calculation is only valid for a hydrochloric acid of 0:1 mol/l (= 0.1N) – or a sulphuric acid solution of 0.05 mol/l (= 0.1 N)

Example 1

Calculation Valid for a hydrochloric acid of 0.1 mol/l or sulphuric acid of 0.05 mol/l (both 0.1 N)

Sample of bath

Factor for

Faktor for

Factor for

NaOH 100 %

NaOH 50 %

NaOH 38 °Be

in g/l

in g/l

in ml/l

in g/l

in ml/l

1 ml

4,000

8,000

5,229

12,099

8,896

2 ml

2,000

4,000

2,614

6,050

4,448

5 ml

0,800

1,600

1,046

2,420

1,779

10 ml

0,400

0,800

0,523

1,210

0,890

For titration of 2ml of bleach liquor with 0.1mol/l HCl-solution Lösung (= 0.1 N) 9.3ml of HClsolution are consumed. How much NaOH 100% in g/l does the bleach liquor contain ? The factor for a sample of 2 ml bleach liquor and NaOH 100% is 2 (see table). g/l NaOH 100% = 9:3 · 2 = 18.6 g/l

Example 2

ml/l or g/l of NaOH x-% = consumption acid solution · factor

For titration of 2ml bleach liquor with HCl solution of 0.1mol/l HCl (= 0,1 N) 9.3 ml HClsolution are consumed. How much NaOH 50% in ml/l does the bleach liquor contain ? The factor for a sample of 2 ml of bleaching liquor and NaOH of 50% is 2.615 (see table). ml/l NaOH 50% = 9.3 · 2.614 = 24.3 ml/l


57

Lab Test Book CHT

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