1. Sodium Chlorite and its Application in the Textile
Industry
Dr. J. J. SHROFF
Research and Development Department, The Arvind Mills Ltd., Ahmedabad-2.
http://www.clo2.com/reading/textile/application.html
Copied on August 16, 2004
Recently, it has been announced that sodium chlorite, a chemical useful for bleaching
textiles and paper pulp, will be produced on large scale for the first time in India. In this
connection, a comprehensive review of the chemistry of sodium chlorite is presented.
INTRODUCTION
BLEACHING of polyester-cotton blend fabrics is mainly required for the cotton
component. However, if pure white goods are to be marketed, the polyester component
also requires a bleaching treatment as the polyester fibres have a slight colouration, as
they are manufactured. The bleaching treatment also becomes essential if sighting colours
which are difficult to remove are used or the polyester fibres have turned yellow during
heat-setting.
BLEACHING AGENTS
Sodium or calcium hypochlorite, hydrogen peroxide or sodium chlorite are the bleaching
agents which can be used with these blend fabrics.
Disadvantages of the hypochlorite bleaching
Whenever cotton fibres are acted upon by either calcium hypochlorite or sodium
hypochlorite, a compound known as oxycellulose tends to form. This degradation product
is objectionable in yarn or cloth because it causes tendering of the fibre, the development
of yellowish or brownish stains on storage and uneven dyeing.
In bleaching cotton goods with hypochlorite, the amount of oxycellulose formed can be
kept down to a minimum by a careful chemical control of every step of the process, and
especially, by stopping the bleaching action before it has gone beyond a certain point.
However, it is ordinarily impossible to prevent completely the formation of oxycellulose.
Advantages of the sodium chlorite bleaching
1. Research work carried out by R&D department of the Mathieson Alkali Works,
Inc., (B.P. 380,488) showed that all danger of forming oxycellulose can be

2. avoided by bleaching the goods by means of sodium chlorite (NaClO,) in an acid
solution instead of using hypochlorite in an alkaline solution. Under acid
conditions of pH 3 and greater, cellulose is not injured and the presence of sodium
chlorite does not change this.
2. Sodium chlorite has sufficient oxidizing power to destroy all the colouring matter
associated with cotton fibre, but it is not powerful enough to attack the fibres
themselves. Hence, it can be used safely, producing better and more permanent
whites without loss of tensile strength.
3. Sodium chlorite is not decomposed rapidly by acid or temperature. It, likewise,
does not react with synthetic detergents to injure the detergent's cleansing
properties. This non-reactivity is mutual and the detergent does not injure the
oxidizing properties of the sodium chlorite or its stability.
4. Hard water does not interfere with the process.
5. Sodium chlorite is very soluble in water, to the extent of about 40 per cent by
weight, at 20°C.
6. Solutions prepared for commercial oxidizing or bleaching processes are extremely
stable.
7. Sodium chlorite oxidizes many of the naturally occurring waxes and pectins in the
cellulose which tends to solubilize them and make for a more even piece of
goods.
8. The bleached material has high absorbency and permanent whiteness.
9. Another very definite advantage is concerned with hand. This is due to the
processing of the fabric entirely on the acid side.
10. The process reduces the total time of bleaching with the corresponding reduction
in handling of the material.
In general, the use of sodium chlorite offers a finishing plant the opportunity of reducing
processing time, and obtaining a superior result at no additional cost and very often at a
reduced cost.
Drawbacks of sodium chlorite-bleaching and preventive measures
There are certain drawbacks with this bleaching agent.
1. Acid solution of sodium chlorite which generates chlorine dioxide (ClO2) has a
great corrosive action on the materials of construction including stainless steel.
Special material such as glass, porcelain, earthenware or some selected plastics
are therefore required for fabricating machinery if sodium chlorite is to be used as
a bleaching agent.
Titanium is the most resistant metal used for this purpose today. In the textile
industry, molybdenum alloy stainless steels are used for acid chlorite bleach
apparatus. Type 316 stainless steel is preferred. For best operation, the stainless
steel sheet should be cold rolled and polished, and all welds should be ground
smooth and polished.

3. The nitrate ion is found to reduce corrosion of the bleaching machinery and is
supposed to have a passivating effect. Addition of 1/2 g/l of sodium nitrate is
therefore recommended to the bleaching bath. Some bleaching auxiliaries, for
example, Bleaching-auxiliary HC and HV (Hoechst) are marketed which have
been found to be useful in preventing corrosion as well as reducing the
objectionable smell of chlorine dioxide. These auxiliaries possibly contain sodium
nitrate which prevents corrosion and a synthetic detergent which gives a foam
cover on the surface of bleaching bath and thereby reduces the trouble of smell. A
double salt of sodium chlorite and sodium nitrate has also received some
commercial acceptance.
2. Fumes of chlorine dioxide (ClO2) are toxic and can cause sickness, lack of
appetite and nausea to the operatives and therefore, effective renewal of air is
essential.
Method of bleaching
Hydrogen peroxide is the major bleaching chemical for textiles. However, in 1960,
sodium chlorite made a new bid in the United States and was adopted for a continuous
bleaching system in a major finishing plant. Contrary to European practices, this
continuous bleaching range consisted of three J-Box operations. First, a 1.5 per cent
caustic soda solution (later, sodium bromite) was applied to the cloth to be steamed 30
minutes for desizing After a rinse, the cloth was saturated with a 3 per cent caustic soda
solution and steamed one hour in a J-Box. The scoured cloth was rinsed and then
saturated with the sodium chlorite solution prior to steaming for one hour in the third J-
Box. The alkaline desize and scour was used in an effort to achieve an outstanding
prepare to reduce the amount of sodium chlorite required for the bleach. An elaborate
control system using caustic soda or phosphoric acid was used to maintain the pH of the
sodium chlorite with a very narrow predetermined range.
The following is a typical formula for bleaching polyester-cotton blend fabrics: 2 g/1
NaClO2, 2 ml/1 formic acid (85%) to adjust pH to 3, 1 g/l NaNO3,.
The goods are treated in an enclosed jig for 1-1.5 hours at boil. An after treatment with
antichlors such as sodium bisulphite (1-2% at 70°C, for 10 minutes) is sometimes
desirable. To remove the colour from motes of cotton it is necessary to use a peroxide
bleach after this treatment.
Commercial sodium chlorite bleaching solution
The commercial sodium chlorite bleaching solution containing, in addition, special
ingredients such as anticorrosive agent. buffering agent, chlorine dioxide fume controller,
stabilizer surfactant and wetting agent is also available as weakly alkaline highly
concentrated solution of 200 gms. sodium chlorite per litre. Thus, a pre-prepared
bleaching solution needs no other bleaching auxiliaries. except acid, for pH control.

4. Anticorrosive agent prevents the corrosion of bleaching equipment constructed from
stainless steel. buffer salts control the liberation of chlorine dioxide produced during the
bleaching process, avoiding the loss of chlorine dioxide. Mixture of surfactant salts has
very good washing, cleaning and penetration effect on soiled goods which are to be
bleached and therefore produces a purer white and stabiliser controls the pH of the bath
during the bleaching process. Such stabilised sodium chlorite bleaching solutions possess
good storability so that stock solution can be kept without loss of active bleaching
substance. Even heating of this leads to hardly any reduction in bleaching power. Thus,
the use of sodium chlorite is economical in operation and highly effective.
Precautions to be observed
Sodium chlorite bleaching solution which is applied should not be allowed to dry on
combustible substances such as wood or paper, since this may lead to outbreaks of fire
due to spontaneous combustion.
Sodium chlorite is a highly effective bleaching agent for the following textile fibres: (1)
Cotton, (2) bast fibres (flax, hemp, jute {used as a delignifying agent for lignocellulosic materials such as jute, wood
pulp etc., the latter process being accompanied by a simultaneous bleaching action}, ramie), (3) man-made fibres, (a)
based on cellulose: viscose filament, viscose staple, cuprammonium filament,
cuprammonium staple, acetato filament, acetate staple. (b) Fully synthetic: polyamide
group, e.g., Nylon, Perlon; polyacrylonitrile group, e.g., Dralon, Orlon, Radon, Dolan:
polyester group, e.g., Dacron, Diolen. Terylene, Trevia; polyvinyl group, e.g., Pe-Ce,
Rhovyl.
It is also suitable for fibre blends and blended fabrics composed of the above mentioned
natural and man-made fibre.
In the following table an attempt is made to summarize different methods of bleaching
with sodium chlorite for various types of fibre including conditions of bleaching.
Manufacture: Since sodium chlorite is manufactured from chlorine dioxide, a short
description of the properties and the processes for the manufacture of chlorine dioxide
will not be out of place here.
Chlorine dioxide
Physical properties: Chlorine dioxides is a gas at ordinary temperatures. It has an intense
greenish-yellow colour, a density of approximately 2.4 and a pungent, irritating odour.
The boiling point of liquid chlorine dioxide is 11°C and its melting point 59°C.
Decomposition: Pure gaseous chlorine dioxide decomposes at a measurable rate at
temperature above 30°C and from 50 to 60°C it decomposes explosively. Chlorine
dioxide is usually handled in dilute mixtures with air in the range of 8-12 per cent by
volume. Spontaneous decomposition can and does occur at this dilution in the presence of
iron rust, grease, and many organic particles. Direct sunlight also causes decomposition.

5. With dilute mixture, the explosions are relatively mild and are referred to in the industry
as "puffs". To take care of "puffs", generators, storage tanks, and bleaching towers are
equipped with explosion lids.
Corrosion: Chlorine dioxide solutions are very corrosive and must be stored in suitably
lined equip" meet. Suitable materials for storage vessels are: (1) glass-lined steel, (2)
fibre glass polyester and (3) til lined steel. Piping pumps valves and lines may be made of
glass, glass-lined, titanium, PVC, Saran, "kel F", "Teflon", and Karbate.
Preparation: Because of its unstable nature, chlorine dioxide is always generated at the
point of use.
There are five principle methods of generating chlorine dioxide which are now in use
throughout the world: (1) The Mathieson process, (3) The Day-kesting process, (4) The
Hooker R-2 process (ER-2 process in Canada), and (5) The Persson process.
The mechanism of the formation of chlorine dioxide from sodium chlorate is the same for
all processes. The fundamental reactions producing chlorine dioxide from chlorates are:
HClO3 + HCl --> HClO2 + HClO
HClO3 + HClO3 --> 2ClO2 + H2O
The R-2 process which is extremely simple to operate and which gives the highest yield
of chlorine dioxide of any commercial process is given below:
The R-2 process: This process, covered by U.S., Patent 2,863,722 issued to W. Howard
Rapson, is assigned to Hooker Chemical Corporation in the U.S.A., and the equivalent
Canadian Patent 543,589 is assigned to Electric Reduction Company in Canada.
The process consists of feeding a solution containing both sodium chlorate and sodium
chloride in essentially equimolar ratio, and concentrated 66° Be sulphuric acid into a
reaction vessel. Air is blown into the bottom of the vessel to provide rapid agitation,
stripping, and dilution of the ClO2 produced. In this process, ClO2 and Cl2 are evolved in
what is nearly a 2 to 1 ratio. The ClO2 is absorbed in a conventional tower with chilled
water. About 25 percent of Cl2 evolved (12 to 15 per cent based on ClO2) dissolves in the
ClO3 solution. The remainder passes through the tower and is picked up as either calcium
or sodium hypochlorite in the second, smaller tower or suitable absorption system. The
yield of ClO2 by the R-2 process is 95 to 96 per cent of the theoretical under-mill
conditions. This process is currently operating in four mills in the U.S.A. and is being
installed in a number of other millet It produces ClO2 at the lowest cost of any process in
mills where full use can be made of the chlorine, salt cake, and effluent acid. Advantages
of the R-2 process are as follows: (1) The process gives the highest yield of ClO2 of any
commercial process. (2) The process is extremely simple to operate. (3) The process
responds immediately to a change in production rate and can be started up from full shut-
down to full steady production in less than 20 minutes. (4) The ClO2 production is strictly
proportional to chlorate fed at all production rates. (5) The process can be run in any

6. existing ClO2 generator and will produce at upto 10 times the rated capacity of the
existing generator. (6) The process can be fully automated to run off a float valve in the
ClO2 storage tank.
Sodium chlorite
In 1921, E. Schmidt discovered that cellulosic fibres can be purified by chlorine dioxide
with no appreciable degradation. This discovery led to extensive ret search to develop
economical methods for bleaching with chlorine dioxide. Being extremely explosive at
high concentrations, chlorine dioxide gas could not be transported as such. It was
necessary to develop a stable chemical which could be safely transported and which
could be easily reacted to form chlorine dioxide at the bleaching site. Mathieson
Chemical Corporation successfully developed sodium chlorite as the economical
commercial chemical for this purpose.
Preparation: Sodium chlorite may be prepared by passing chlorine dioxide through a
moderately strong solution of sodium hydroxide.
2 ClO3 + 2 NaOH --> NaClO2 + NaClO3 + H2O
However, sodium chlorate is formed in an equimolar quantity and is difficult to separate.
The formation of chlorate may be minimized by adding reducing agents to the alkali. For
example, in the presence of sulphur or sodium sulphate, a high yield of sodium chlorite is
obtained. In an early method, carbonaceous matter such as animal charcoal, sugar, coke,
wood saw dust, paper pulp etc., nitrogen compounds such as ammonia, or one of a range
of compounds containing the NH2 or CN group were used for the reduction. Following
the chlorate reduction, the sodium chlorite solution is evaporated and drum dried.
Suitable reducing conditions are obtained if an aqueous solution of chlorine dioxide is
treated with sodium amalgam (Na 0.1%), hydrogen peroxide or sodium peroxide. Sodium
chlorite is formed witH negligible amounts of sodium chlorate. Since the mercury
cathode of an alkali chloride electrolyte cell can serve as the amalgam, this process is
clearly capable of large scale application. Sodium chlorite may also be prepared by
passing chlorine dioxide into a solution and allowing it to bubble over a cathode at which
hydrogen (nascent) is being evolved. Formation of chloric acid is much reduced and the
unstable chlorous acid immediately reacts with alkali to give the more stable chlorite.
On a large scale it is convenient to absorb the chlorine dioxide in an aqueous solution
containing hydrogen peroxide and the alkali metal bicarbonate preferably at about 25°.
Purification: Because of large differences in solubility between chlorite and other related
salts, fractional crystallisation provides a useful means of purifying metal chlorites.
Anhydrous sodium chlorite: To prepare anhydrous sodium chlorite, the trihydrate is made
into a slurry with water at 38°, and the solution saturated at this temperature is separated
and cooled to 25° when the anhydrous salt crystallises.

7. Important properties of sodium chlorite
1. The anhydrous salt is not hygroscopic and samples have been kept for ten years
with only slight loss.
2. Heating for 30 minutes at 150°C causes no explosion.
3. The decomposition temperature varies with moisture content, being 202°C with
3.7% of water, and 177°C. with 10.7% of water.
4. The mode of decomposition of aqueous solutions is profoundly influenced by the
pH of the solution. In alkaline solution sodium chlorite is stable in the absence of
light. However. for pH values less than 7, the rate of decomposition increases
considerably with decrease in pH. Decomposition is very slow at pH values above
4.6. The decomposition of sodium chlorite in neutral solution can be accelerated
by metallic catalysts, the decomposition rate increases with increase in
temperature and quantity of catalyst.
5. The reactions of chlorites are considerably modified in the presence of chlorine or
hypochlorites. The action of chlorine on sodium chlorite is a preparative method
for chlorine dioxide. With sodium hypochlorite, the products are sodium chlorate
and chlorine dioxide, in a ratio depending on the pH of the solution. Thus, at pH2
chlorine dioxide is liberated while in alkaline solutions chlorate is formed
exclusively. The relative amounts of chlorate and chlorine dioxide produced also
on the chlorite/hypochlorite ratio of the reactants. When this ratio is 2:1, chlorine
dioxide predominates. On increasing ratio beyond 1:1 immediate chlorate
formation occurs. While with a ratio of 1:4 the chlorine dioxide is completely
converted to chlorate within 30 minutes at room temperature.
6. The action of certain reducing agents, such as aldehydes on sodium chlorite yields
chlorine dioxide, with iodides and iodine.
3 HClO3+ I- --> 2IO3 + 3 Cl- + 3H+
This forms the basis of the analytical determination of chlorites.
7. Oxidizing agent if sufficiently strong, will oxidize chlorite to chlorate. In neutral
solution oxidation by potassium permanganate proceeds according to the
equation:
3 ClO2- + 2 MnO-4, + H2O --> 3 ClO-3 + 2MnO2, + 2 OH-
ESTIMATION
Estimation of sodium chlorite in bleaching solution
Theory: Determination of sodium chlorite is Carried out by iodometric means and
proceeds in accordance with the following reactions:
2NaClO2 + 8KI + 4H2SO4 = 2NaCl + 4K2SO4 8I + 4H2OI 8I + 8Na2S203 = 8NaI +
4Na2S4O6

8. This means that:
2NaClO2 = 8I= 8Na2S2O3
or NaClO2= 4Na2S2O3
Reagents required: (i) 10 per cent potassium iodide (A.R.) solution in distilled water. (ii)
5 per cent sulphuric acid (A.R.). (iii) O.1N sodium thiosulphate solution.
Determination of sodium chlorite (solid)
Procedure: One gm. of sodium chlorite is dissolved in distilled water and is made upto
1000 ml. with distilled water. 50 ml. of this solution is allowed to run, while shaking the
flask into 10 ml. of the 10% potassium iodide solution, and the whole is subsequently
acidified with 10 ml. 10% sulphuric acid. The reaction mixture is left to stand for 3
minutes in dark and is then titrated with O.1N sodium thiosulphate solution, until pale
yellow colour is obtained. After adding about 1 ml. starch solution, titration is continued
until the solution becomes colourless. After titration the solution should have acid
reaction to congo red paper.
Calculation: ml. of O.1N sodium thiosulphate solution consumed x 4.52 = per cent of
sodium chlorite.
Determination of sodium chlorite in solution containing upto 10 g/l. sodium chlorite
Procedure: An Erlenmeyer flask of 100 ml. capacity is first charged with about 10 ml.
potassium iodide solution followed by exactly 10 ml. of the sodium chlorite solution to
be tested and the whole is then acidified with about 10 ml. of 5 per cent sulphuric acid.
The reaction mixture is left to stand for 3 minutes in the dark and is then titrated with
O.1N sodium thiosulphate solution until a pale yellow colour is obtained. After adding I
ml. starch the solution, titration is continued until the solution become colourless.
Calculation: Ml. of O.IN sodium thiosulphate solution consumed x 0.226. = g/l. sodium
chlorite.
Determination of sodium chlorite in solution containing more than 10 g/l. sodium
chlorite
Procedure: Determination is carried out as described above with the exception that only 1
ml. of sodium chlorite solution is used.
Calculation: ml. of O.IN sodium thiosulphate solution consumed x 2.26 = g/1. sodium
chlorite.
Determination of sodium chlorite in solution containing more t~ 100 g/L sodium
chlorite

9. Procedure: From sodium chlorite solution, 1 ml. is removed with a pipette and diluted in
a 100 ml. volumetric flask upto the mark. Take 10 ml. from this for estimation.
Determination is carried out as described above.
Calculation: ml. of O.1N sodium thiosulphate solution consumed x 22.6 = g/1. sodium
chlorite.
Determination of chlorine dioxide produced in bleaching of textiles with sodium
chlorite
Chlorine dioxide reacts with H-acid at pH 4.1 to 4.3, to form a pinkish blue, light
sensitive compound having an absorption maximum at 525 mµ. Addition of ferric
chloride increases the colour intensity and of malonic acid eliminates the interference of
free Cl.
For determination, 90 mL of the bleach liquor, after treatment with 5 ml. of acetate buffer
of pH 4.1 to 4.3 and I ml. of FeCI3 solution (10 mg/l) is made upto 100 ml. Free Cl is
removed by adding 2 ml. of 1% malonic acid solution and keeping aside for 20 minutes
in the dark. If any turbidity is formed it should be removed by addition of ZnSO4 and
NaCH. To this, 0.4 ml. of H-acid reagent (0.85 g. H- acid dissolved in 5O ml. of boiling
enthanediol and diluted with to 100 ml.) is added and the extinction is measured at 525
mµ after keeping the solution in the dark. Phosphates, if present, interfere and hence
corrected calibration graph should be used.
BIBLlOGRAPY
1. Kulkarni, G.G., and Trivedi, S.S., Processing of Polyester Cotton Blends, ATIRA
(1967).
2. Taylor, M.C., White, J.F., Vincent, G.P., and Cunningham, G.L., "Sodium
Chlorite; Properties and Reactions," Industrial and Engineering Chemistry 32,
No. 7, 899-903 (July 1940).
3. White, J.F., Taylor, M.C., and Vincent, G.P., "Chemistry of Chlorites," Industrial
and Engincering Chemistry, 34, No. 7., 782-792 (July 1942).
4. Dubeau, A.L., MacMahon, J.D., and Vincent, G.P., "A New Oxidizing Agent,"
Am. Dyestuff Reptr., 28, 590-592 (1939).
5. Vincent, G.P., "Textone," Am. Dyestuff Reptr., 29, 269-271 (1940).
6. Vincent, G.P., Dubeau, A.L, and Ivey, J.W., "The Treatment of Spun Rayons with
Textone," Am. Dyestuff Reptr., 29, 296-299 (1940).
7. Vincent, G.P., Dubeau, A.L., Synan, J.F., "BIeaching Cotton Goods with Textone
Activated with Hypochlorite," Am. Dyestuff Rcptr., 30, 358-360 (1941)
8. Sneed, M C., Maynard, J.L., Brasted, R.C., "Comprehensive Inorganic
Chemistry," Vol. 3, D. Van Nostrand Co., Inc, (1954).
9. Remy, H., "Treatise on Inorganic Chemistry," Vol. 1, Elsevier (1956).
10. Wood, C.W., and Holliday, A.K., "Inorganic Chemistry," Butterworths (1963).
11. Partington, J.R., "General and Inorganic Chemistry," MacMillan and Co., Ltd.,
(1954).

10. 12. Salus S, O.E., "Chlorates by Electrolysis of Alkaline Chlorides the Effect of Some
Factors," Bol. Soc. Chilena Quim. 4, 43 (1952); Chem. Abstr., 17, 9823 (1953)
13. Sconce, J.S., "Chlorine, its Manufacture, Properties and Uses," American
Chemical Society, Monograph Series, Reinhold, (1967}
14. Rapson, W.H., Tappi, 41, 181 (1958); U.S.P. 2, 863, 722.
15. Patridge, H.D., and Rapson, W.H., "Mill Trials of R-2 Proccss," Hooker Bulletin
262; Tappi, 44, No. 10 (1961).
16. Mellor, J.W., "Comprehensive Treatise on Inorganic and Theoretical Chemistry,"
(supplement II) Part.I, Longmans (1956).
17. Yntema, L.F., and Fleming, T., "Volumetric Oxidation of lodide to Iodate by
Sodium Chlorite,"Ind. Eng. Chem. Anal., 11, 375-7 (1939).
TABLE
Material Machinery Liquor: Sodium pH value Bleaching Remarks
and material material chlorite of liquor
of ratio and acid to
construction be used
1. Loose cotton Molybdenum- 5:1 20 kg. 5: 3.5 hours at Residual
(1000 kg) stainless steel Sulphuric 80-85°C concentration
or stoneware acid 1:10 (176-185°F), of sodium
with verticle heating in chlorite 0.2 g/l.
circulation first 2 hours For full white a
from 40-80°C subsequent
(104-176°F) bleach may be
necessary with
4 kg. hydrogen
peroxide 35%
by weight 2.0
g/l. 2 hours at
85 °C (185°F).
2. Cotton yarn Stainless steel 4:1 16 kg. 3.8-4.0; 3 hours at Residual
(1000 kg) with verticle Formic 85°C concentration
Mercerised circulation acid or (185°F), of sodium
treated with acetic acid. heating in chlorite 0.2 g/l.
hydrochloric first 2 hours Rinse: warm
acid and from 40-85°C and cold,
rinsed. (104-185°F) optical
whitening the
Blankophor
BA in batches
on a Gerber
hank dyeing
machine.
3. Cotton Molybdenum 12:1 4 kg. 3.5-3.8 1 hour at Rinse: hot and
cheese 34/2 steel V-14A Formic 90-95°C cold. Optical

11. (250 kg) type closed acid or (194-203°F) whitening with
cheese acetic acid. heating in Blankophor
bleaching first 30 BA.
machine with minutes from
radial 40-90°C
circulation (104-194°F)
4. Viscose Closed winch, 20:1 1.6gm. 3.5; Formic 20-30 If suction
staple fibre stainless steel acid 85% minutes at ventilation is
(100 kg) 316 80-85°C lacking, raise
(176-185°F) temperature in
30 minutes
from 40-80°C
(104-176°F)
and bleach for
10-15 minutes
at this
temperature.
5. Viscose Closed winch, 25:1 12 kg. 3.5; Formic Speed of Subsequent
muslin (3000 steel 316. Liquor acid 85% goods: 70 m/ additions
kg) Continuous (3000 litres 2500 minute. which consist
bleach. capacity) litres Treatment of 12.0 kg.
Goods time: 15 Sodium
in the minutes. chlorite and
beck Total 1.5 litre, 85%
100 kg. bleaching Formic acid
time 15 should flow
minutes. continuously
Temperature: into the
85°C (185°F) bleaching bath
through a
metering
device. If the
chlorite
bleaching
proper is given
on several
winches,
subsequent
additions are
often made
only to the first
one, and the
second winch
is merely kept
to a pH of 3.5

12. by the addition
of acid. This
continuous
bleach can be
combined with
pre-treatment
of the viscose
staple to form
a continuous
process.
6. Viscose Stainless steel 4:1 8 kg. 3.5-3.8; Heat to Rinse: warm
staple fabric 316 with Formic 75-80°C and cold.
(2000kg) pump and acid 85% (167-176°F)
enzymatically, circulation and bleach
desized, pipes of for 1 hour at
scoured on a stainless steel. this
rope soaper. temperature.
7. Visco Closed jig. 4:1 640 gm. 3.5-3.8;For 4-5 passages
filament and Stainless steel mic acid at 75-80° C
acetate 316. 85% (167-176°F)
filament union
fabrics (100
kg)
8. Nylon fabric Closed jig. 8:1 12.5 4; Acetic 4-6 passages
(50 kg) Stainless steel gm. acid 60% at 80-85°C
316 type. (176-185°F)
9. Perlon (50 Winch 30:1 1.2 kg. 3.8; Acetic Heat in 30
kg) soiled stainless acid 60% minutes from
steel-316. 40-85°
(104-203°F);
30 minutes
85°C (185°F)
10. Acrylic Stainless 30-40:1 1.2-2.0 2.5-3.0; Heat in 30 If a full white
fibres steel-316. g/l. Oxalic acid minutes from is desired on
solution 1-2 g/l, 40-95°C acrylic fibres,
added in solution, (104-203°F); optical
portion. added in 30 minutes at whitening with
portion. 95-98°C 2.5 %
(203-208°F). Blanlcophor
ACF on weight
of goods is
advisable.
Blankophor
DCB ultrafine

13. (now replaced
by Blankophor
DBS) is highly
suitable for the
optical
whitening of
acrylic fibres
in an after
treatment
operation.
11. Polyester 1.2-2.0 1.0-3.0 g/l. Heat in 30
fibres g/l. Oxalic acid minutes from
added in solution 40-95°C
portion added in (104-203°F)
portion 30 minutes at
95-98°C
(203-208°F).