730
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 42, No. 4
addition of calcium chloride tends t o reverse the relative volatility
TABLE 111. SMOOTHED VAPOR-LIQUID EQUILIBRIUM ARD BOILof acetic acid and water. The reversal takes place a t about 8 ING POINT DATAFOR ACETICACID-WATER-CALCIUM CHLORIDE weight % calcium chloride in the liquid phase and it is possible, SYSTEM (Pressure, 760 mm. Hg)
“t. %
S 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5.0
10.0
10.0 10.0 10.0 10.0 10.0 10.0 10.0
10.0 10.0
10.0 10.0 20.0 20.0 20.0
20.0 20.0 20.0 20.0 20.0 20.0 20.0
20.0
20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 95.0 5.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 95.0 5.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 95.0
8.5
16.5 30.3 41.8 52.5 62.2 70.7 78.2
85.5
92.8 96.3 4.5 9.0 18.2 27.6 37.2 46.8 56.8 67.0 77.5 88.2 93.8 3.3 6.5
13.0 19.6 26.2 33.7 42.3 53.2 67.0 81.6 90.0
T , C. 111 . 0 108,2 105.1 103.4 102.3 101.7 101.2 100.8 100,5 100.2 100.0
iii:~
109.3 107.0 105.4 104.2 103.5 102,8 102.3 102.0 101.8 , . .
ii4:6 112.1 110.1 108.4 107.0 105.9 104.9 104,4
104.5
r_
S
ii
30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 50.0 50.0 50.0 50.0 50.0 60.0 60.0 60.0 60.0 60.0
5,0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 95.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 95.0 60.0 70.0 80.0 90.0 95.0 90.0 92 5 95.0 97.0 99.0
Y 2.4 4.9 10.0 15.1 20.6 26.5 33.8 42.6 53.6 71.5 84.5 12.0 16.5 21.7 27.7 35.0 44.6 61,5 76.5 21.0 26.9 36.5 53.2 69.0 46.5 52.0 59 2 67.0 81.0
..
.. ..
..
..
..
.. .,
..
T, C .
...
...
ii9:0
116.8 114.5 112.8 111.5 110.6 110.2 110.3 125.0 122.1 120.0 118.3 116.9 116.3 117.0 117.8 127,5 125,s 124.8 125.1 126.2 134.7 135.0 136.5 138.0 140.0
. .
...
...
because of the lack of available data on the boiling points of solutions of calcium chloride in glacial acetic acid. CONCLUSIONS
The results confirm the observation of Quartaroli (9) that the
by the addition of moderate quantities of calcium chloride, to obtain a reversed relative volatility which is greater in magnitude than that for the ordinary distillation. In order to explore fully the potentialities of such a separation process, further work on the continuous extractive distillation a>pect will be required. NOMENCLATURE
S
= weight per cent calcium chloride in liquid T = temperature, C. X = weight per cent water in liquid (salt-free basis) Y = weight per cent water in vapor LITERATURE CITED
(1) Davidson, A. W., J . Am. Chem. Soc., 50, 1890 (19238). ( 2 ) Hall, 11‘. T., “ T e x t b o o k of Quantitative Analysis,” pp. 150-1, New York, J o h n Wiley & . Sons, Inc., 1941. (3) “ I n t e r n a t i o n a l Critical T a b l e s , ” Vol. 111, p. 325, New York, McGraw-Hill Book Co., 1928. (4) Jones, C. il., Schoenborn, E. M., a n d Colburn, A. P., IND. Ex.. CHEX, 35, 666 (1943). (5) M c B a i n , J. W., a n d K a m , J., J . Chem. Soc., 115, 1332 (1919). (6) M e n s c h u t k i n , B. N., 2. anorg. Chem., 54, 89 (1907). (7) O t h m e r , D . F., and Gilmont, R., IND.EXG.CHEY.,36, 1061 (1944). (8) Perry, J. H., ed., “Chemical Engineers’ H a n d b o o k , ” p. 1360, New York, McGraw-Hill Book Co., 1941. (9) Quartaroli, A., Ann. chim. applicata, 33, 141 (1943). (10) S h r e w , R. N., “Chemical Process Industries,” pp. 682-8, New Y o r k , McGraw-Hill Book Co., 1945. RECEIVED July 27, 1949. Presented before the Oklahoma State Meeting of the American Institute of Chemical Engineers, Stillwater, Okla., November 12, 1949.
Sa
te CARL J. MALM, LEO J. TANGHE, AND GLENN D. SMITH Eastman Kodak Company, Rochester, !V. Y .
Salt effect is a measure of the increase in viscosity of cellulose acetate caused by the presence of certain salts. A procedure for the measurement of the salt effect has been developed. The influence of salts on viscosity depends on: the nature of the salt; amount of salt; pH of the solution from which the salt is applied; solvent for the cellulose acetate in solution; degree of hydrolysis of cellulose acetate; and the amounts of carboxyl and combined sulfate in the cellulose acetate.
T
HE term “salt effect” is used in this paper to designate the
ratio of the viscosity of one portion of a cellulose acetate washed with water containing a certain salt to the viscosity of a second portion of the same acetate washed with salt-free water or with water containing a salt known to have no effect on the viscosity. I n general, salts of monovalent cations-e.g., sodium chloride-are without effect on the viscosity, whereas salts of polyvalent cations-e.g., calcium chloride-increase the viscosity. This behavior was observed in cellulose acetate by Rogovin (8) who found a salt effect in acetone but not in formic acid. Lohmann ( 6 ) has studied the salt effect in a variety of solvents and found that i t was manifested especially in concentrated solutions in solvents such as ketones and esters which do not
contain hydroxjl groups. The salt effect in acetone was reduced by the addition of water or methanol. High viscosity, due either to high solids content or to high molecular weight of the cellulose acetate, increased the effect. He observed the salt effect mainly Kith calcium chloride and found that it increased with the amount of salt added. An especially significant observation was that the increased viscosity of cellulose acetate due to certain salts did not add to the tensile strength of fibers spun from these solutions. Other findings in this field have been that the salt effect was more pronounced with products made from wood pulp than from cotton linters (4). Also, it increased with the degree of hydrolysis of the cellulose ester (3) and with the p H of the wash solution from which the salts are applied ( 7 ) . Lohmann’s finding that the increased viscosity due to salts failed to give a corresponding increase in the yarn strength makes this increase in viscosity undesirable. With this background an investigation was undertaken to develop a procedure for measuring salt effect and to establish factors responsible for the effect. First, several of the above observations were verified using production batches of yarn-type cellulose acetate containing approximately 39% acetyl. Table I gives the effect of various salts on the viscosity of this type of cellulose acetates. The acetates of the alkaline earth elements all gave about the same
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
April 1950
131
p H of the rinse solution. Probably most trivalent salts are ineffective because of the low p H of their solutions. From the data of the above tables i t is apparent that a method Viscosity, Poises for comparing the salt effects of different products must of necesSalta From Pulpb From Linters 6 sity be empirical, with all details of treatment carefully standAcetates ardized. 46.2 46.4 62.8 62.4 Sodium The first step is the removal of any salts already present Magnesium 70.6 70.6 71.1 71.9 Calcium 66.3 67.3 68.8 68.6 in the cellulose acetate. Cellulose acetate made with sulfuric Strontium 72.6 73.1 71.1 71.6 Barium 72.8 73.9 72.4 72.2 acid catalyst is preferably dried in the presence of small amounts Zinc 48.0 48.4 of stabilizing salts, These salts were removed by rinsing in dilute 101 103 ... Lead 44.6 44.4 Chromium ... acid, in distilled water, or by reprecipitation of the cellulose 63.3 63.0 Aluminum, basic . . . Chlorides acetate from acetone solution into acidified distilled water. The 45.8 46.0 58.2 58.4 Sodium latter method was preferred because i t permitted filtration of the Magnesium 55.0 54.7 56.2 57.2 Calcium 63,l 62.1 74.9 77.1 solution of the ester to remove any insoluble particles. Acetic 70.1 Strontium 69.1 87.0 84.2 56.2 Barium 56.2 60.9 60.6 acid (1to 2oJ0)and the common mineral acids such as hydrochloric, Carbonates nitric, sulfuric, and phosphoric (0.1 to 0.2%) in distilled water 59.3 58.6 84.6 79.9 Sodium 73.1 73.0 80.0 80.0 Magnesiumc were satisfactory. Acetic acid was used in most of the present 6 9 . 4 7 0 . 0 69.6 6 9 . 6 Calciumc Sulfates work. 44.6 44.6 57.1 56.9 Sodium Calcium acetate was chosen over calcium chloride for evaluatr Magnesium 46.5 47.4 60.5 60.6 42.2 43.1 60.1 59.2 CalciumC ing the salt effect, since the viscosity of samples treated with Drying at Room Temp. in Desiccator calcium acetate showed less variation with the amount of salt ... ... None 42.1 42.3 and with the p H of the rinse solution. Two rinses in sequence Sodium chloride 42.1 43.1 ... ... were made in order to allow the cellulose acetate to come to Two rinses in 0.001 M salt solution o r suspension. b Double viscosity values supplied t o aid in appraising the work. equilibrium with the solution. Additional rinses were found to C Suspensions of salts stirred 15 minutes before adding cellulose acetate. be without further effect on the viscosity. The time of the second rinse was varied from 15 minutes to 8 hours, but maximum viscosity was reached after 30 minutes. Variation in temperaresponse, but n-ith the chlorides the effect increased in the series ture from 0' to 100" C. was without effect on the viscosity when magnesium through strontium and then dropped off with barium. the time of rinsing was 1 hour. After the second rinse the celluOf several trivalent salts and hydroxides tried, only basic alumilose acetate was pressed to a definite wet weight so that the num acetate gave a salt effect. Lohmann ( 2 ) found no salt same amount of salt solution was always left on the sample. effect with trivalent salts. According to Table I1 sodium chloAs is shown in Table IV, the salt effect increases slightly with the ride was without effect on the viscosity over a wide range of conconcentration of ester in solution, but the viscosities were detercentration of salt in the rinse solution. Calcium acetate gave mined a t solids concentration of 5 to 1 in acetone, instead of the a moderate and calcium chloride a sharp increase in viscosity somewhat higher concentrations used in actual spinning operawith respect to concentration of salt. Table I11 shows that caltions, in order to facilitate handling of solutions and measurecium chloride was more sensitive than calcium acetate to the ment of viscosities. Parallel runs were always made with a salt which displayed no effect on viscosity. Sodium chloride or sodium acetate was used for this purpose. The use of salt-free TABLE 11. EFFECT OF THE AMOUNT OF SALT ON CELLULOSE material for viscosity measurements was avoided because of ACETATE VISCOSITY possible loss in viscosity due to degradation during drying. Molarity Viscosity, Poises Source of Salt-treated samples, however, could be dried for over 16 hours Cellulose of Rinse NaCl C,aCI? Ca(.OAo)z .4cetate Solution rinse rinse rinse a t 100" C. without any loss of viscosity.
TABLE1. EFFECT O F VARIOUS SALTS ON THE VISCOSITIES CELLULOSE ACETATES FROM PULP AND LINTERS
OF
(1
Pulp
0.0005
51.2 52.2 51.6 52.3 49.2 49.8 49.9 51.2 49.9 51.6 58.4 59.8 59.6 60.4 59.9 59.9 59.8 61.0 58.0 59.6
0.001 0.002 0.005 0.010 0.0005
Linters
0.001 0.002 0.005 0,010
TABLE 111. EFFECT OF pH
60.7 61.7 69.0 68.3 87.0 87.2 158 157 277 266 68.0 67.0 72.8 72.2 90.7 91.4 146 146 240 242
70.3 71.0 77.2 76.8 79.4 79.0 83.0 85.0 85.7 86.9 77.8 78.3 80.0 79.4 82.2 81.8 84.4 84.4 87.2 87.5
SALTRINSE SOLUTION ON VISCOSITY OF CELLULOSE ACETATE OF
Addition to PH Adjust pHa Viscosity, 4.0 5 ml. AcOH 51.3 4.5 0.5ml.AcOH 62.6 5.0 10 ml. Ca(0H)zb 64.8 5.5 30 ml Ca 0H)zb 64.0 50 rnl: Cat0H)zb 63.9 6.0 0.001 M CaClz 4.0 1dropaoncd.HCl 48.8 4.5 None 49.5 5.0 4 m l Ca 0 H ) t 51.5 5.5 10 ml: Ca!OH)z 59.6 6.0 13 ml. C a ( 0 H ) t 69.8 a In 5 liters of solution, before addition of cellulose acetate. b Saturated solution of Ca(0H)Z.
Rinsing Salt 0.001 M Ca (0Ac)z
Poises 55.6 63.2 63.9 63.8 64.5 48.4 50.3 51.9 58.3 68.6
__ OF CELLULOSE ESTERCONCENTRATION TABLEIV. EFFECT ON SALTEFFECT
% Solids 2.5
THE
Source of Cellulose Acetate Pulp
5.0
Pulp
7.5
Pulp
10.0
Pulp
12.5
Pulp
15.0
Pulp
17.5
Pulp
20.0
Pulp
22.5
Pulp
2.5 5.0
Linters Linters
7.5 10.0
Linters Linters
12.5 15.0
Linters Linters
17.5 20.0
Linters Linters
22.5
Linters
Vincosity, Poises Ca(,OAc)n NaCl rinse rinse 0.0334 0,0397 0.0336 0.241 0.276 0.238 0.288 0.965 1.18 1.10 0.944 3.29 4.19 3.27 4.30 8.95 11.0 8.57 26.5 35.2 26.6 37.3 60.1 95.4 61.2 144 242 146 237 333 670 342 0.0425 0.0450 0.316 0,348 0.318 0.350 1,26 1.41 4.37 4.46 4.31 4.49 11.9 13.3 35.3 39.2 39.6 35.0 82.4 101 191 245 240 190 240 440 571
___
Salt Effect 1.18
1.18 1.23 1.30 1.26 1.36 1.58 1.66 1.98 1.06 1.10 1.12 1.03 1.12 1.12 1.23 1.28 1.30
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
732 220
but samples of high viscosity oft,en required a longer time. 1%cosities on all samples were run in duplicate. Samples treated with sodium chloride or sodium acetate to determine the base viscosity were always run concurrently with other sahtreated samples. S o n e of the viscosities was run until the \Thole set was ready. The solutions were poured as rapidly as possible to minimize loss of solvent into test tubes 32 X 200 mm., and the viscosities measured at 25 + 0.1 C. by the falling ball method. All the viscosities except those in Table V were run in acetone. The solvent-solid ratio was 5 t o 1 except in Table IV.
PI
20 20
30
40
60
50
70
Hours Hydrolysis a t IOO'E
Figure 1.
Salt Effect of Pulp Cellulose Acetate during Hydrolysis MEASURERIENT O F SALT EFFECT
T ~ y ohundred grams of cellulose acetate SALTTREATMEKT. were dissolved in 2 t o 3 liters of acetone and the solution filtered through felt on a Biichner funnel. The cellulose acetate was precipitated by pouring in a thin stream into 270 acetic acid in distilled water with vigorous stirring, and was washed t o neutrality in distilled water. The wet precipitate vias divided into two equal parts, one of which n-as stirred in 5 liters of distilled water to which 5 ml. of 1 M calcium acetate solution had been added. The other part was given a parallel treatment with sodium chloride or sodium acetate solution. After 15 minutes the cellulose acetate was separated from the rinse solution, fresh rinse solution was supplied, and the stirring was continued for 1 hour. The cellulose acetate was then squeezed out in a cloth bag to a net wet weight of 400 =t20 grams and dried in a current of warm air a t 65" C. ~IEASUREMENT OF VISCOSITY. Samples of 16 grams of cellulose acetate were weighed into tared 8-ounce screwcap bot,tles and dried 4 hours a t 100" to 105' C. with the caps removed. The caps were tightened during cooling to room temperature. A small amount of sample mas then removed to bring t,he sample weight to 15.62 =t0.02 grams t o yield a 5 t o 1 solution n-ith 100 ml. (78.1 grams) of acetone delivered from an automatic dispensing pipet, jacketed .cvith circulating water a t 25" =t0.1 O c. The water content of the acetone was previously adjusted to 0.40 i: 0.05%. Satisfactory closures were obtained by wrapping the liners with 0.0015-inch tin foil and tightening the cap securely. The bottles mere then tumbled until all the cellulose acetate dissolved. Samples of low viscosity dissolved overnight,
TABLE v.
E F F E C T O F S O L V E N T O N S.4LT EFFECT OF C E L L U L O S E A C E T A T E FROM P U L P
Solvent Acetone-water series. % water None addeda 0.25 1.00
2.0 4.0
8.0 Acetqne-methanol aeries, yomethanol 2.0
Salt Effect
Using samples salt-treated as described above, the salt effert, of cellulose acetate made from wood pulp and cotton linters was measured over a wide range of concentration (Table IV), and an increase in salt effect was observed as the concentration of cellulose acetate in solution increased. At concentrations below 0.25y0 solids, salts TF-ere without effect on the viscosity. In Table 5: the salt effect of cellulose acetate from pulp is shon-n in several solvents. KO salt effect was found in acetic acid. The addition of water or methanol to acetone lowered the salt effect. Table 'ST1 and Figure 1 show the variation in salt effect of cellulose acetate from pulp throughout its acetone soluble range of hyBorderline solubility a t eit,her end of the range i n i s e to high viscosities and high salt effects.
T.4BLx 171. S.4LT EFFECT D U R I N G HYDROLYSIS OF CELLULO~E X C E T A T E FROM P U L P
Hours of Hydrolysisa 15
Viscosity, Poises ;\:aC: C,aC12 Salt rinse rinse Effect 3 oe 663 2.17 309 67 1 36.6 41.6 20 55.3 1.50 36.5 54.5 41.2 31.9 22 43.4 1.33 31.9 43 0 40.5 36.9 30 1.33 48.8 36.e 48.7 40.1 39.1 35 67.1 1.40 39.3 57.6 39.4 46.4 40 66.7 1.42 46.1 66.5 53.2 39.1 45 82 6 1.56 52.8 52.9 62.2 38.7 50 96.6 1.55 82.1 96.5 38 2 55 106 68.4 1.54 104 67.8 81.0 37.9 1.60 GO 130 . . ~ 130 37.3 1.72 64 90.8 158 92.3 157 36.7 112 1.91 69 2 15 114 217 a Temp. 100' F.; initial water content of hydrolysis bath, 8 % ; amount of sulfuric a d d , 7%, based on original amount of cellulose. CF /c
Acetyl 42.3
~
,
EFFECT O F CARBOXYL GROUPS 48.9
49,7
45.2 48.6 46.5 46.3 43.1 43.2 41.3 41.4 41.7 42.2
68.1 69.2 68.1 68.6 62.2 62.0 54.8 54.1 50.9 48.7 46.8 47.0
1.40
P .41 1.34 1.26 1.21 1.12
43.3 64.3 1.41 45.0 63.5 44.3 55.9 1.28 43.4 56.2 5s. 0 47.9 51.8 1.08 46.6 50.4 fEthyiene chloride: 420 505 1.15 methanol (9O:lO) 460 508 Methyl acetate 228 225 Pyridine 116 115 Aoetic acid 750 I I U 757 T h e acetone contained 0.35% water in addition t o the amount added.
.4.0
6
Viscosity, Poises SaCl Ca(,Ohc)z rinse rinse
Vol. 42, No.
Cellulose acetate made from wood pulp shoa ed consiotently greater salt effect than cellulose acetate of approximately the same degree of polymerization made from cotton linters. This is evident from Tables I, 11, and IT. Since wood pulp contains slightly more carboxyl groups than cotton linters, cellulose acetate made from cotton linters was subjected to a mild oxidation with potassium permanganate to determine whether an increased salt effect would result. It was found that small amounts of carboxyl group increased the salt effect tremendously, and a correlation was observed between the salt effect and the amount of carboxyl introduced (Table VI1 and Figure 2). Some of these products were oxidized further with chlorous acid to convert any aldehyde groups, generated by the permanganate, to carboxvl groups (9). Apparently the aldehyde groups do not influence the salt effect, since the graph of carboxyl versus logarithm of the salt effect gives points on the same straight line regardless of the presence of aldehyde groups. Treatment of cellulose acetate with chlorous acid wlthout prior oxidation with potassium permanganate was found to be without effect on the carboxyl content.
April 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
ON TABLE VII. EFFECTOF OXIDATION
SALT EFFECT OF CELLULOSE
THE
ACETATE
A ~ O H HCIOl Cellulose Pulp
... ...
None
Viscosity, Poises NaCl Ca(,OAc)z rinse rinse
Oxidized
62.7
44.0
NO
58.4 58.2 X O 55.7 0.125 99.5 56.2 No 57.8 0.25 99.5 57.3 NO 62.7 0.50 99.5 62.4 NO 63.5 0.10 80 62.8 62.6 Yes 62.7 No 0.25 59.4 80 59.3 Yes 58.1 68.4 No 57.2 0.50 80 57.2 Yes 51.0 51.4 NO 38.9 1.00 80 39.1 Yes 35.3 35.5 a Grams per 100 grams of cellulose acetate.
Linters
*
KhInOP
Solvent
None
NO
68.8 68.6 87.6 88.9 106 106 291 298 91.4 92.4 171 154 155 154 319 316 730 706 2630 2610 5000 4330 Too high to measure
Salt Effect 1.44
% COOH
1.58
0.036 0.033 0.018 0.020 0.028
0.037 0.038 0.018 0.020 0.023
1.84
0.037
0.034
4.72
0.49
0.055
1.22
733
and after contact with the sample. By comparing this method with the silver ion displacement method (IO)and the calcium acetate method (11) for measuring the carboxyl content of oxidized cellulose, i t was found that both valences of the barium were utilized in salt formation with the carboxyl groups. OXIDATION OF CELLULOSE ACETATE
Six hundred grams of cellulose acetate, made from purified cotton linters, were dissolved in 6 liters of 80% acetic acid, and potaesium perman1.45 0.033 0.030 ganate was added with good stirring. The amount 2.78 0.047 0.038 of permanganate was varied from 0.10 to 1.00 gram per 100 grams of cellulose acetate to intro2.61 0.046 0.047 duce different amounts of carboxyl (Table VII). 4.45 0.061 0.066 Some oxidations were carried out in glacial acetic acid instead of 80% acetic acid, and smaller 12.5 0.082 0.083 amounts of carboxvl were introduced. After 51 0.108 0.108 stirring for 3 hours-at room temperature the residual manganese dioxide was decolorized with 0.131 0.134 120 sodium bisulfite. The oxidized cellulose acetate 0.157 0.153 ... was precipitated and washed to neutrality in d i e tilled water. Half of the wet roduct was oxidized! further with chlorous acid. $or this purpose an oxidizing bath was prepared by dissolving 300 grams of sodium chlorite and 800 ml. of acetic acid in 12 liters of distilled water. The perman-' ganate oxidiaed product was stirred in this mixture for 1 hour Reducing groups and large amounts of easily hydrolyzed acetyl a t room temperature and then washed to neutrality. Both groups interfere with the determination of small amounts of oxidized parts were divided into three aliquots containing apcarboxyl in cellulose acetate. Methods depending simply on proximately 100 grams of cellulose acetate, dry basis. Oneacid-base titration in the presence of the sample did not give portion was dried and used for carboxyl determinations. Tha remaining portions were treated with 0.001 M solutions of satisfactory end points. The silver o-nitrophenolate method (IO) sodium chloride and calcium acetate, respectively. has the disadvantage that the reagent is unstable due to a slow deposition of silver from solution. Also, reducing groups in the I n order to determine the effect of location of the carboxyl sample release some metallic silver from the solution and thereby group in cellulose, two samples of cellulose acetate were separated register partly as carboxyl (1,6). into fractions of low and high viscosity. Portions of each fracThe carboxyl determinations reported herein were made by tion were oxidized (Table VIII) and blends were prepared with ion displacement with barium o-nitrophenolate: the added carboxyl on the low and high fractions, respectively. The blends with the carboxyl on the high viscosity fractions ex2 cellulose-COOH Ba(0-C6H,--NOz)2 + hibited considerably more salt effect (Table IX). (~ellulose-CO0)~Ba 2HO-C,Hl-N02
+
+
The concentration of barium ion in solution was measured before TABLEIVIII. OXIDATION OF FRACTIONATED CELLULOSE ACETATEI Sample
Viscosity
KR
