a DANIEL FRISHMAN, LYDIA HORXSTEIN, ARTHUR L. SMITH, AND 3IILTCBN NdRRBS Harris Research Luborutories, V u s h i n g t o n 11, D .
w o o l can be made resistant to shrinkage during laundering by treatment with solutions of active chlorine. The pH of such solutions is of importance in determining the type and extent of modification of the wool. The oxidation potentials of these solutions decrease with increasing pH, and the extent of modification of the fiber is found to be an inverse function of pH. The rate of reaction is also dependent upon pH and in addition the rates indicate that different types of reaction occur in the regions of pH 1, 3 to 7, and 9 to 11. The weight loss during treatment; allzali solubility; cystine, sulfur, and nitrogen contents; and acid- and base-binding capacities of the treated and untreated fibers confirm the difference between the reactions i n these pH ranges. These data indicate that the treatment of wool with solutions of active chlorine can be most advantageously performed in the region of pH 8 to 9.
T
HAT wool can be made resist,antto shrinkage during laundering by treatment with active chlorine has been known for many years, and for this reason the reaction between wool and “active” chlorine is of great interest t o the textile industry. (Substances containing positive univalent chlorine atoms are designated as active chlorine compounds, because of their oxidizing power and general reactivity.) I n spite of the fact that the reaction b e k e e n active chlorine and wool has been studied since the early part’ of the century, the actual reaction mechanism has not been understood clearly. This can be attributed in part t o the fact that’ much of the earlier work was concerned only with the practical aspects of shrinkproofing rather than with the study of reaction mechanisms. However, many fundamental observations have been made which are of considerable value in the further elucidation of the reaction of wool with active chlorine. The most obvious result of the reaction is the destruction of the wool fiber when excessive quantities of active chlorine are used. Presumably, this is due in part t o attack on the cystine which is in agreement with observations of early workers that chlorine attacks the cystine sulfur. Thus, Trotman and Wyche (29)noted that the sulfur was attacked and formed sulfuric acid. The liberation of sulfur in the form of sulfides (21) and sulfuryl chloride (9) has also been postulated. Harris and Smith (5, 61 showed that wool treated wit,h hypochlorites has a lower cystine content than untreated wool and t h a t the allrali solubility of oxidized wool is a quantitative measure of the extent of modification. Earlier, Trotman ( 2 7 ) and 8obue and Hirano (3s) showed qualitatively that the alkali solubility of v-001 is increased on treatment with active chlorine. The participation of the nitrogen in n.001 in this reaction has also been demonstrated. Trot,man (E?),as m-ell as voni Hove ( 7 ) and others, reported chloramine formation and the loss of nit,rogen, although the presence of chloramines in the treated ~ o o has l been a controversial point,. I n 1906 Vignon and Mollard (3g) reported that “chlorine is not fixed by the wool,” but later Trotman (28)
(1.
claimed that chloramines are formed vhen chlorine in the form of chlorine water, rather than hypochlorous acid, is used in the reaction. I n a recent publication Lemin and T’ickerstaff ( I f ) claimed that chlorine gas reacting with wool forms a negligible amount of chloramines. Disagreement among invest’igatorsalso occurs in regard to the dyeing properties of wool treated with active chlorine. Xercer, in the middle of the 19th century, noted that wool treated \Tit,h chlorine had an increased affinity for dyes, and Trotman ( 2 6 ) , vom Hove ( 7 ) , and niany others later substantiated this finding. However, as early as 1903 Johnson (8) noted t8hatthe trcatmcnt of wool with dilute alkaline hypochlorit,e solutions decreased thc: affinity of the fibers for acid dyes. Recently Kienle, Royer, and McCleary (IO) have studied the rate of dyeing of chlorinated samples and have found that the pH of the solution of active chlorine used in treating the ~ o o does l affect the ratc of dyeing. Lemin and Vickerstaff (11) report an increased rate of dyeing for an acid dye on wool treated with chlorine gas, but their therm+ dynamic calculations based on equilibrium data indicated that the affinity of the dye for the treated and untreated wool was substantially the same. It has long been recognized that the reaction between wool and active chlorine is very rapid. This results in B prefcrential attack of the outermost layers of the wool fibers and many investigators have shown that’ the surface frictional properties and microscopic appearance of the fibers may change. It has also been shown ( 4 ) that the change in mechanical properties may be quantitatively accounted for by the depth of penetration of the active chlorine into the fiber. This brief review serves t o emphasize the dependence of the course of the reaction between wool and active chlorine on the conditions of treatment. Preliminary experiments demonstrat’cd that the pH of the solutions of active chlorine is of prime importance in determining the type and extent of modification attained, and therefore EL more comprehensive study of this reaction a t different p H values was made. The present paper describes the resulbs of this study. METHODS
The experimental conditions were planned to conform, in a general \T ay, to certain textile practices which produce wool whose tendency to fclt is greatly reduced. The fiber was immersed in a suitable aqueous solution and the hypochlorite added slowly in order to assure uniformity of treatment. There are, of course, many other methods for the treatment of m-001 with aqueous solutions of active chlorine, but the effect of varying the pH should be essentially the same in all methods.
EXPERIMENTAL METHOD. T o o l yarns were treated with solutions of sodium hypochlorite containing 9% of available chlorine (4.5y0 active chlorine) on the weight of the wool. This rather high concentration of chlorine was used so that the extent of the chemical and physical modification of the treated fibers could be more accurately determined. The treatments were made for a period of 90 minutes in baths buffered a t p H values ranging from 1.1to 10.7 a t 25 O C. The buffers which were used follow: phos-
2280
December 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
phate buffer at p H 3.1, 7.14, and 10.7; acetate buffer at p H 5.2; borax buffer at p H 9.2, and 1% hydrochloric acid a t p H 1.1. These buffers are described by Clark ( d ) . The sodium hypochlorite was added a t a uniform rate for 30 minutes and the treating bath was analyzed for active chlorine every 5 minutes. T h e wool remained in the treating solution for a total of 90 minutes i n all cases, although at the lower pH’s the reaction was substantially completed after the first 30 minutes. The wool was then thoroughly rinsed and air dried. ~ZNALYTICALMETHODS. T h e per cent available chlorine in the solution was determined by adding standard arsenite to an aliquot of t h e solution and back-titrating the excess arsenite with iodine. I n order to test the treated wool for the presence of active chlorine, t h e wool sample was placed in the arsenite solution for 5 hours and the arsenite was titrated with iodine. I n some large scale treatments, the treating bath was analyzed for chloramines by a modification of the method of Van der Meulen,(SI). The treated samples and controls were then subjected to the following analyses: cystine analyses by the Sullivan method (d6), sulfur analyses by oxygen-bomb method (121, alliali-solubility analyses by the method of Harris and Smith ( 5 ) ,and nitrogen analyses by a micro-Kjeldahl method. T o measure the acidbinding capacity, samples of treated and untreated wool were washed in distilled water for 48 hours, dried, and placed in 0.1 h’ hydrochloric acid for 24 hours at 25 O C. Aliquots of the solution were then titrated with sodium hydroxide, using bromocresol purple indicator. To determine the base-binding capacity the samples were first washed in distilled water for 24 hours, dried, and then placed in 0.1 N sodium hydroxide for 24 hours at 0 ” C. Aliquots were titrated with hydrochloric acid. Since alkali hydrolyzes the wool protein, aliquots of the solution were analyzed for nitrogen by the micro-Kjeldahl method in order t o determine the amount of dissolved protein. A suitable (small) correction t o the alkali-binding capacity was then made on the basis of these results (24). The effect of the treatments on the load-elongation behavior of wool was determined by measurements on single fibers before and after treatment. T h e general procedure has been described elsewhere (4). The change in load-elongation properties is described by the ‘‘307, index,” which is the ratio of the energy required t o stretch a wet fiber to 30% elongation after a treatment divided by t h e energy required to stretch a wet fiber to 30% elongation prior to the treatment. The compressional resilience, which is essentially a measure of the recoverability of fabric or yarns when subjected to “squeezing,” was determined as described by Schiefer (22). hlETHOD O F D E T E R V I N I N G OXIDATION POTENTIALS. Remington and Trimble (17) and others (16, $0, SO) have reported the oxidation potentials of hypochlorite solutions over a wide range of pH. Remington and Trimble ( 1 7 ) had demonstrated also that buffers have specific effects upon the oxidation potentials. Therefore, the oxidation potential of the hypochlorite solutions were determined with the buffers used in this investigation. These measurements were made with a platinum electrode and a saturated calomel electrode but suitable correction was made so that the reported values refer to the standard hydrogen electrode. The potentials were determined at 25” C. and were recorded at various concentrations of available chlorine. The oxidation potential increased very rapidly with concentration a t relatively low values then became constant. Since the maximum potential was attained at low concentrations, this potential was chosen as characteristic of the oxidizing system. The values reported in this paper are in good agreement with values found in the literature. RESULTS AND DISCUSSION
%ai
100 0
g
90
0
2
a
80
w
z_ 7 0 [L
0
2
60
V -1
50 40
0 pH 1 1 4 pH31 0 pH52
0 pH74 0 pH 92 0 pH107
W
10
0
13
20
33
40
50
60
70
80
TIME IN MINUTES
Figure 1. Rate of Reaction between Sodium Hypochlorite and Wool a t Various pH Values
periments is shown in Figure 1. Since the chlorine mas added over a period of 30 minutes, the slope of the curve representing the treatment at p H 1.1 indicates t h a t the rate of reaction between the wool and the active chlorine was so rapid t h a t there was virtually no titratable chlorine in the solution a t any time. I n agreement with Phillips (I@, the rate of reaction is shown t o increase with decreasing pH, but it should be noted that the data obtained a t p H 9.2 and 10.7 fall on one curve; those at p H 7.4, 5.2, and 3.1 form a second curve; and that a t pII 1.1 a third curve. I n contrast, the oxidation potentials of these solutions, shown in Figure 2, increased rather uniformly with decreasing pH. The fact t h a t the rates indicate three different reactions over the range of p H 1 through 11 is significant, and, as will be shown below, the results of the chemical analyses of the treated fibers confirm the presence of three somewhat different reactions a t the pH’s noted. MECHANICAL PROPERTIES OP TREATED ANI) UNTREATED WOOL.The oxidation potential also determines the degree of modification of the reducing substance. When the oxidation potentials shown in Figure 2 were plotted against the logarithm of the change in the stress-strain propertics of thc wool fibers (100 minus 30% index), as shown in Figure 3, a straight line is found. Since the change in stress-strain properties or 30% index (Table I) is a good measure of the over-all modification of the wool fibers, it is evident that the Oxidation potential of the active chlorine solution and in turn the pH have considerable influence on the extent of the reaction. As may be expected, the compressional resilience of the yarns show the same general change with the p H of treatment as does the 30% index. SULFCRAND CYSTINE CONTENT. Tho sulfur, nitrogen, and ovstine contents of the treated samdes are in all cases less than the respective values for the untreated wool (Table I). This indicates t h a t in addition t o a loss in weight during treatment as shown in Table I, there is further preferential attack of the sulfur
The analyses of the treated and untreated wool are presented in Table I. However, the interpretation of these data is dependent on additional information which ma3 collected during the course of the investigation, and it is the interplay of both sets of data and, wherever necessary, TABLE I. RESULTS O F NALYSES 0I F UNTREATED .4ND TREATED T.s’ O O L their presentation in graphic form which permit the developAcidBasement of a unified description pH of Cystine Sulfur Binding Binding Sitrogen 30% Content, Content, Content, Capacity TreatCapacity, Index, of the reaction between active ment Me./G. ’ Me./G. % % % 70 chlorine and wool. 1.1 9.9 21.0 8.9 3.08 15.64 0.72 0.7% 84 RATEOF REACTION,OXIDA3.1 2.9 36.7 7.8 3.12 15.68 0.66 0.97 85 5.2 -2.0 35.3 7.6 3.2% 15.54 0.61 0.98 88 TION POTENTIAL, AND pH. 7.4 0 23.3 8.2 3.37 15.59 0.64 93 0.93 9 2 2.8 15.7 9.8 3.26 15.69 0.72 0.78 97 The rate at which the wool re3.1 13.1 10.7 3.27 15.62 10.1 0.72 0.74 96 acts with active chlorine under Untreated 3.42 ... 14.3 15.97 10.9 0.76 0.64 99 the conditions of these ex-
Compressional
Resilience, % 51 50 53 52 55 57 57
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
2282
proximates t h a t of the untreated wool. Therefore, it would appear t h a t the sulfur is lost as sulfide or elementary sulfur, and Wright (84) has shown t h a t alkaline hypochlorite solutions react with cystine t o form polysulfides. The destruction of the disulfide group in alkaline solution Kith no hypochlorit,e present is also known to yield sulfides ( I S ) . NITROGEN.As shown in Table I, small losses of nitrogen were obtained at all pH’s. The reactivity of amino nitrogen with active chlorine is TT ell knoJ5-n and specifically in thc case of wool, Whewell and Selim (33) showed t h a t fibers deaminated with nitrous acid react n ith less active chlorine than untreated wool. Thus, the loss in nitrogen may in part be attributed to the oxidation of the amino groups as shown in the folloning reactions:
I.4
1.2-
-9
1.1
-
Id
-
J
-
0.9
-I
2 0.8L
t-
g 0.7z 0.6-
5 g 0.50.4
--CHgNH2
PH
Figure 2. Oxidation Potential of Sodium Hypochlorite Solutions as a Function of pH
and nitrogen. The cystine content shows the greatest decrease but inspection of the cystine to sulfur ratio (Table 11) reveals that the decrease in cystine content does not result in a corresponding loss in sulfur. This suggests that the cystine sulfur is oxidized tiy the active chlorine but that the sulfur is not split from the nool, and indeed Consden et al. (5) report that analysis of dry chlorinated wool by partition chromatography indicated the presence of cysteic acid. The formation of some ovidized cystine derivative should result in a gain in weight of the wool and, as shown in the treatment at p H 5.2, when the cystine to sulfur ratio is lowcst, the wool does increase in weight. The production of strong acid groups in the wool is indicated by the increased base-binding capacity and the decreased acid-binding capacity of the treated wool, as shown in Table I and Figure 4. As nil1 be discussed later, this change in the acid- and base-binding capacities is due probably t o the attack of amino groups as well as t o the oxidation of cystine sulfur. Aside from the oxidation of cystine sulfur to form comhined cysteic acid or some other oxidation product, there is also a loss in sulfur which occurs t o the greatest extent at the lowest pH’s. This may account for the formation of sulfuric acid in the reaction between wool and chlorine as has been reported (69). The mechanism of the oxidation reaction at the lower pH’s may be different and result in the loss of sulfur due to the presence of dissolved chlorine. Ridge and Little (18)calculated the relative concentrations of chlorine, hypochlorous acid, and the hypochlorite ion at different pH’s and found t h a t the active chlorine is present mainly as hypochlorous acid between the p H 2 and 8, but at lower pH’s chlorine predominates and a t higher pH’s, the hypochlorite ion. The oxidation of sulfur dioxide by chlorine results in the formation of chlorosulfonic acid, which hydrolyzes to sulfuric acid; Justin-Mueller (9) proposed t h a t this type of reaction occurs between chlorine and wool. I n contrast t o the results obtained a t p H 7.4 and below, the cystine t o sulfur ratio of wool treated in the alkaline region ap-
TABLE 11. RATIOS OF NITROGEN TO SULFUR AND CYSTINETO SULFUR IN UNTREATED AND TREATED WOOL pH of Treatment 1.1 3.1 5.2 7.4 9.2
10.7 Untreated
Vol. 40, No. 12
Nitrogen t o Sulfur Ratio 5.1 5.0 4.8 4.6 4.8 4.8 4.7
Cystine to Sulfur Ratio 2.9 2.5 2.3 2.4 3.0
8.1 3.2
+ Clz -+
-CHzNHCl+
HzO --+ -CHO --+ -COO11
T h e loss of amino nitrogen and the formation of acidic groups would result in a decrease in the acid-binding capacity and a n increase in the base-binding capacity. I n fact, more nitrogen is lost than can be accounted for by the decrease in acid-binding capacity of the wool. As indicated above, hoTyever, there is also evidence t h a t strongly acidic groups are formed from the oxidation of the cystine sulfur and the latter would also contribute t o similar changes in the acid- and base-binding capacities. The relative contributions of each of these factors to the changes in the acid- and base-binding capacities were not determincd.
Figure 3. Logarithm of Decrease i n 30qo Index as a Function of Oxidation Potential
Loss
IPS
WEIGHT DURIXG TREATMENT AND ALKALI SOLU-
The loss in weight during treatment and the alkali solubility of the treated sample are frequently used in studying the action of oxidizing agents on wool. However, it is apparent from Figure 5 that in this case there is an inverse relationship between these two quantities and t h a t therefore neither of these tests can individually characterize the extent of fiber modification. Thus, wool treated with active chlorine at between p H 3 and 8 may show only a slight change in weight, but the cystine contents and alkali solubility of these treated samples indicate extensive modification of the fiber. The loss in weight during treatment is a complicated function of the oxidation potential and the mechanism of the reaction. At p H 1, where the oxidation potential is high, the weight loss is at a maximum; at intermediate p H values, the weight loss is small and some of this is probably compensated for by the addition of oxygen t o the fiber, as suggested above. I n the alkaline region BILITY.
December 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
1.001 little, if any, compensation occurs b u t the reaction is mild because of the 0.95low oxidation potential, and only small losses in g0.90weight occur. u i The alkali solubility is 90.85a n indication of t h e 22 . change in the chemical gFeo constitution caused by oxidizing agents of the 5!; wool and seems to be m0.75m W closely related to the cystine content. I n Figure 6, the alkali soluiE0.75. bility of the oxidized wool 5 samples is shown as a 2 80.70 function of the cystine content. [ H a r r i s a n d z 20.65Smith ( 5 ) demonstrated 90 a n inverse, linear relaD tionship between alkali solubility and cystine content for wool exposed to the carbon arc.] The results of the two tests, loss in weight during t r e a t m e n t a n d alkali solubility, correlate with the change in mechanical properties of the wool fibers. A measurable loss in weight will undoubtedly tend t o weaken the fiber just as decreasing its diarneter would weaken it. The alkali solubility indirectly measures the number of attacked cystine residues and i t has been shown by many investigators t h a t the disulfide cross links are largely responsible for the exceptional mechanical properties of the wet wool fiber. Thus, if the loss in weight is high, as occurs when wool is treated with solutions of active chlorine a t pH 1.1, or if the alkali solubility is much increased over that of the untreated wool as a t p H 3.1, 5.2, and 7.4,a change in mechanical properties can be expected, and as shown in Table I, both the 30% index and compressional resilience are substantially decreased at these pH’s. For practical purposes it is desirable to produce shrink-resistant wool with a minimum of fiber modification. Therefore, i t is of interest t o examine the data and to determine the most desirable conditions for the treatment of wool. The curves shown in Figure 5 indicate t h a t at very low pH’s the loss in weight is high, . at p H 3 t o about 7 the alkali solubility is high, and a t pH’s above 9 the loss in weight tends t o increase and the possibility of alkali damage t o the wool is present. It would appear, therefore, t h a t the most advantageous conditions for the treatment of wool with active chlorine could be found in the regions of p H 8 t o 9, and indeed further experiments in the laboratory and in the plant indicate t h a t the use of hypochlorite solutions at p H 8 t o 9, under controlled conditions, results in shrink-resistant wool with a minimum of fiber modification. PRESENCE OF CHLORAMINES. As indicated previously, the presence of chloramines in the treated wool is a matter of conjecture. Their presence in the samples treated in the laboratory could not be demonstrated. However, in separate rather large scale experiments, chloramines were present in the bath. With insufficientrinsing, i t is therefore possible that they might be found in the wool. Another possible explanation for the disagreement i n the literature can be found in the work of Wright (34, 36). H e found that the course of the reaction between active chlorine solutions and amino acids or soluble proteins is dependent 011 the relative concentrations of the reactants. When the ratio of amino acid or protein to active chlorine i’s large, no active chlurine
2283
1
(3
-
-
(3
v
I
I
I
2
I
3
I
4
I
5
I 6
I
7
1
8
1
9
1 I 1011
PH
Figure 5. The Loss in Weight during Treatment and the Alkali Solubility as a Function of the pH of the Hypochlorite Treating Solution
is destroyed; rat,her, chloramines %re formed and the reaction then ceases. But., when the active chlorine is in excess, the reaction proceeds to the dichloramine stage and finally oxidation of the amino acid, resulting in the loss of active chlorine. Norman (14) found that carbon dioxide, nitrogen, and water are formed from glycine when an excess of active chlorine is present. DYEING PROPERTIES OF CHLORINATED WOOL. The decreased acid-binding capacity of the samples treated with active chlorine might be expected to decrease the affinity of the wool for acid dyes and it has been shown t h a t mild treatments with alkaline solutions of active chlorine will decrease the rate of dyeing (8, 1B). However, i t has long been m o w n t h a t under most conditions of treatment chlorine will increase the rate of dyeing of wool. This apparently anomalous situation can be explained on the basis of the reaction of the chlorine with the surface of the fibers. The scales or cuticle of a wool fiber is a barrier to the penetration of the dye molecules into the cortex and Carter and Consden
k
35 30
E
-
F
E
2
m
2.5-
3
J
0
e?
- 204 Y -I
15-
0
CYSTINE
I I 95 90 C O N T E N T (%)
I 10.0
Figure 6. The Alkali Solubility as a Function of the Cystine Content
2284
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40, No. 12 wool rr-as negative but chloramines mere found in the treating solution during a large scale treatment,, and the conditions of treatment of wool x i t h solutions of nc Live chlorine influenced the rate of dyeing of the treated saniplcs. Under most conditions the ratre of dyeing is increascd, while under very mild conrlitions l,he rate is dccwaxcd. LITERATCRE CITED
(1: Carter, E. G., andConsden, Ii., J . Testile Inst., 37, T227-36 (1Y4G). (2) Clark, W. M., "Tho Deterinination of Hydrogen Ions," 2nd ed., Baltimore, The W j l h i n s & Wilkins Co., 1928. (3) Consden, li., Gorden, A . H., and Mart,in, A. J . P., Biochem. J . , 40, 500-2 (1946). (4) Frishman, D., Smith, A. L., and Harris, M., Textile Research J . , 16, 160-2 (1946). ( 5 ) Harris, M., and Smith, A . L., J . Research, S a t . Bur. S t a n d a d s , 17, 577-83 Figure 7. P h o t o m i c r o g r a p h s of a n U n t r e a t e d Fiber and of Fibers Treated w i t h Sodium (1936). Hypochlorite Solutions a t Different pH Values (6)Ibid.., 18., 623-8 (19371. (7) Hove, H. vom, Angew. Chem., 47,756-62 (1934). Johnson, J. Y., Brit. Patent 4175 (Jan. 8, 1903). ( 1 ) shom-ed that removal of the suriaco scales from ti fiber by Justin-Mueller. E., Reu. gln. mat. color., 41, 78-86 (1037). mechanical scraping is sufficient to increase the rat,t of dyeing. IGenle, R. II., Ro.yer, G. L., and McClears., 11. B., Am. Dilestuf Inspection of fiber photographs made from samples treated with Reptr., 34,42-53 (1945). solutions of active chlorine a t different pH's (Figure 7 ) indicates c 11'1 Lemin, D. R , , Vickerstaff, T., Society of Dyers and Colourists, Fibrous Protein Symposium, pp. 129-41 (May 1946). that in the acidic solutions there is indeed marked destruction (12) hiease, R. T., J . Research, *Vat. B u r . Standards, 13, 617 (1934). of the scales. This may account for the increased rate of dyeing (13) Mizell, L., and Harris, Milton, Ihid.. 30, 47-53 (1943). for the saniples so t'reated. (14) Norman, M .F., Biochem. J . , 30, 484-96 (1936). SUMMARY (15) Phillips, H., J . Textile I n s t . , 37, P302-16 (1946). (16) Randell, hI., and Young, L. E., J . Am. Chem. Soc., 50, 989 The reaction between wool and solutions of active chlorine (1924). has been described in three different pH ranges, and may be (171 Remington, 1'. H., and Trimble, €1. h l . , J . Phys. Ch.em,., 33, sumniariaed as follows: 424-34 (1929). (18) Ridge, B. P., and Little, A. H., J . Textile Inst., 33, T33-68 1. Treatment of n-ool with solutions of active chlorine a t pH (1942). 1 results in a large weight loss, destruction of the surface scale (19) Royer, G . L., private communication, March 14, 1945. structure, and a change in mechanical properties. Although (20) Rius, A., Rev. m a d . cienc. M a d r i d , 26, 142-72 (1931). cystine is destroyed with subsequent, loss of sulfur, the cystine (21) Ruasina, H., X e l l i a n d Teztilber, 12, 404-6 (1931); 13, 207-9 content of the wool treated at pH 1 is actually higher than that of (1932). other samples treated beloTv about pH 8. ( 2 2 ) Schiefer, H. F., J . Research X a t . Bur. Standards, 10, 705-13 2. Wool treated with solutions of active chlorine a t pH 3 to 7 (1933). shows either a slight loss or slight gain in xeight, but the mechani(23) Sobue and Hirano, J . SOC.C h e m I n d . , J a p a n , 37,427-30 (1934) cal properties as well as the appearance of the fiber indicate that extensive modification has occurred. The cystine content is (24) Steinhardt, J., and Harris, Milton, J . Research Nut. Bur. Stnndlowest and the alkali solubility is highest in this p H range. The ards, 24, 335-367 (1940). sulfur loss is small compared to the cystine loss, indicating that (25) Sulli.i.an, M.X., Public Health Re& 86 (1930). the oxidized sulfur groups rcmain in the treated mool. A further 3 6 ) Trotman, S.R., J . SOC.Chem. I n d . , 41, 219-24T (1922). indication of the extensive modificat'ion that has occurred is pro(27) Trotman, 8.R., Textile M e r c z u y , 82, 429, 479 (1930). vidpd by the large changes in acid- and base-binding capacity of (28) Trotman, S. R., Trotman, E. R., and Brown, J., Ibid., 47, 4-8T the samples treated in this pH range. (1928). 3. Treatment of wool with solutions of active chlorine a t pH (29) Trotman, S.R., and Wyche, C. R., I b i d . , 43, 293T (1924). 9 t o 11 results in a slight loss in weight and only minor modifica(30) Turner, H . A., Nabar, G. M.,and Scholefield, F., J . Soc. Dyer8 tion of the wool protein. The scales appear to be unaffected and Colourists, 53, 5 (1937). there is only a slight change in t.he mechanical properties. Al(31) Van der Meulen, P. A., Chem. Weelcblad, 31, 558-61 (1934). though there is a slight loss in cystine, it can be almost quantita(32) Vignon, L., and Mollard, J., Compt. rend., 142, 1343-5 (1906). tively accounted for by the loss in sulfur. (33) Whemell, C. S., and Selim, A., J. SOC.Chem. Ind., 63, 121-3 4. These data indicate that the treatment of wool with solu( 1944) tions of active chlorine a t pH 8 to 9 results in only slight modifica(34) Wright, N. C . , Biochem. J., 20, 524-32 (1926). tion of the fibers. Additional work in the laboratory and in the (35) Tbid., 30, 1661-7 (1936). plant using aqueous hypochlorite solutions a t pH 8 to 9 under .
I
.
cont,rolled condit,ions has further demonstrated that wool can be made shrink resistant with a minimum of fiber modification under these conditions. Other characteristics of wool treated with solutions of active chlorine were investigated and i t was found that: The nitrogen contents of all the treated samples were somewhat lower than that of the untreated control, the test for active chlorine in the treated
RECEIVED Xovember 18, 1947. Presented before the Division of Cellulose SOCIETY, New Chemistry at the 112th Meeting of the ANEREAXCHEMICAL York, N. Y. This article is one of a series dealing with technical phases of the work on shrink-resistant wool, being carried out i n cooperation with the Research and Development Branch of the Office of the Quartermaster General.
,
