ANALYTICAL EDITIOK
MARCH 15, 1940
Fleischer, W. E., J . Gen. Physiol., 18, 473 (1935). Fraps, G. S.,and Kemmerer, A. R., J . Assoc. Oficial Agr. Chem., 22, 190 (1939). Godnew, T. N.,and Kalischewicz, S. W., Planta, 25, 194 (1936). Guthrie, J. D., Bm. J . Botany, 15, 86 (1928). Hegsted, D. M., Porter, J. IT., and Peterson, W.H., IND.Exo. CHEM., d n a l . Ed., 11, 256 (1939). (8) Johnston, E. S., and Weintraub, R. L., Smithsonian Inst. Pull., Misc. Collections 98, KO. 19 (July 31, 1939). (9) Kozminski, Z., Trans. Viaconsin Acad. Sci., 31, 411 (1938). (10) Munsey, V. E., J . Asroc. Oficial A g r . Chem., 20, 459 (1937) ; 21, 6'76 (1938).
151
(11) Scherts, F. M., Plant Phgsiol., 3, 21 1 (1928). (12) Ibid., 3, 323 (1928). (13) Ulvin, G. B., Ibid., 9, 59 (19341. (14) Willstatter, R., and Stoll, A,, "Investigations 3n Chlorophyll",
by Schertr and Merz, Lancaster, Penna., Science Press Printing Co., 1926.
THISpaper includes a portion of the work carried on by R. Wolman in fulfillment of the requirements for the A1.Y. degree a t Michigan State College. This research was supported in part by funds from the Horace H. Rackham Endowment Fund for studies on the industrial utilization of agricultural products. Published with the permission of the Director of the Experiment Station as Journal Article S o . 389 n. s,
Fluidity of Cotton in Dimethyl Dibenzyl Ammonium Hydroxide Measure of Cotton Degradation W. WALKER RUSSELL
I
AND
NORMAN T. WOODBERRY, Metcalf Laboratory, Brown University, Providence, R. I.
T IS now generally recognized that the fluidity (or vis-
cosity) of a solution, prepared by carefully dissolving cellulose in a suitable solvent, is the most sensitive means of analysis for degradation in cellulose. As early as 1911 Ost (62)found that the viscosity of cellulose dissolved in cuprammonium hydroxide solution varied according to the degree of chemical modification of the cellulose. Thus he showed that the viscosity was lowered when the cellulose solute had been previously attacked-for example, by mild oxidation, the action of heat, the action of acids or alkalies a t high temperatures. More detailed studies by Gibson and coworkers (15, 16), Joyner ( I @ , Farrow and Neale ( I d ) , and especially Clibbens and collaborators (3, 4,5, 7-10) later showed the quantitative relationships existing between amount and type of chemical modification suffered by cotton-e. g., due to oxycellulose or hydrocellulose formationand the fluidity of the modified cotton in cuprammonium hydroxide solution. The work cited has also shown that fluidity measurements are capable of detecting and evaluating chemical degradation in cellulose where other methods fail. It is unfortunate that the difficulties associated m-ith the preparation and use of the cuprammonium hydroxide solution, according t o standard methods (1, 7 , 10, 1 7 , 20), have tended to prevent the fluidity method from coming into the general use which i t merits as a n analytical and control method in the many industries where the quality of the cellulose used or produced is important. According to such standard methods the cuprammonium hydroxide solution is tedious t o prepare, must be adjusted to a definite copper, arnmonia, and nitrite content, and then must be preserved in the dark, under an atmosphere of nitrogen, near a temperature of 20" C. Furthermore, the cellulose must be dissolved by agitation with this solvent out of contact with the air for periods u p to 24 hours, during which time the temperature should not vary much from 20" C. Also, because the subsequent fluidity measurement must be conducted without contact with air, i t is usually impossible to obtain check measurements upon a single solution. Fabel ( l a ) , however, has reported a rapid cuprammonium fluidity method of limited applicability in which no effort is made to exclude air, and i t is understood that further
modifications of standard methods are in use in technical practice. The degree of chemical modification of cellulose has also been measured by nitrating cellulose and determining the fluidity of its acetone solution (11, 21). The viscosity of cellulose may be measured in phosphoric acid solution (26), but here measurements are complicated by the relatively rapid rate at which hydrolysis occurs. Some quaternary organic bases are known to be cellulose solvents. Furthermore, Lieser (19) has found t h a t the minimum concentration of base necessary to dissolve cellulose decreases almost linearly as the molecular weight of the organic base increases. Since very stable quaternary compounds (24) of relatively high molecular weight and strong basic properties are now commercially available (the Tritons manufactured by Rohm & Haas Co., Philadelphia, Penna.), i t was thought desirable to investigate the possibility of substituting a t least one of them for the cuprammonium hydroxide solvent in t h e fluidity evaluation of chemically modified celluloses. Because of the unique properties ( I S , 26) which have been attributed to cuprammonium as a cellulose solvent, i t was b y no means certain that such a substitution could be made. However, on the basis of a considerable number of experiments in which dimethyl di.benzy1 ammonium hydroxide (Triton F) has been used in place of cuprammonium hydroxide, it appears that this substitution can be made with considerable success; the fluidity method then becomes a very simple and relatively rapid method of cellulose analysis.
Apparatus VISCOMETER.The viscometers used were of the type described by Cannon and Fenske (6) in their Figure l. This viscometer is designed so that there is no appreciable kinetic energy correction for liquids having viscosities of 2 centistokes or more, and in the present work the solutions exhibited values of at least 23 centistokes. Furthermore, other viscometer errors (loading, drainage, surface tension, etc.) are negligible for ordinary work. All the fluidities reported here were measured xith a viscometer capillary of 1.8-mm. bore. Three standard substances were wed in calibrating the viscometer at 25' C. Aniline, boiling at 184' * 0.2" C., whose density was determined to be 1.0175 at 25' C. (1.0173, International Critical Tables) was assumed to have a viscosity of 3.77 centipoises (27). This aniline was used to calibrate a similar viscometer, whose capillary was 1 mm. in diameter, which was
INDUSTRIAL AND ENGINEERING CHEMISTRY
152
used to standardize a highly purified petroleum oil and also a glycerol solution described below. These solutions were then used to calibrate the larger capillary viscometer. This viscometer was also calibrated directly with two standard liquids. Reagent grade glycerol was diluted with deaerated distilled water to an apparent specific gravity a t 25"/25" C. of 1.20824, corresponding to 79.63 per cent of glycerol and a viscosity of 44.07 centipoises ( 2 5 ) . The other liquid used for calibration was an aqueous solution of reagent grade sucrose made up to contain 59.97 per cent of sucrose by weight. The density of this solution was determined to be 1.28450 a t 25" C. which corresponds to a 60.08 2er cent sucrose solution and a viscosity of 44.02 centipoises ( 2 ) . These standard liquids, in the order mentioned, gave the following viscometer constants at 25" C.: 0.01009, 0.01010, 0.01027, and 0.01002, or an average constant of 0.01012 which was the value used. All viscometer measurements were carried out in a mechanically stirred glass thermostat whose temperature was manually maintained at 25" * 0.1" C. Time was taken with split-second stop watches calibrated against a synchronous motor timer. APPARATUS FOR DISSOLVIKG THE CELLCLOSESAMPLE. As is clear from Figure 1, the cellulose is dissolved in a shortened test tube about 80 mm. deep and 18 mm. wide by rapid stirring with a glass rod 5 mm. in diameter, bent as shown to revolve almost in contact with the inner test tube walls. The glass stirrer is directly attached to the shaft of a small stirring motor whose speed is regulated by a sliding rheostat, The temperature of the solution may be readily controlled by immersing the test tubes in a water bath during the dissolving operation.
VOL. 12. NO. 3
When present, starch n a5 removed from the cotton samples by steeping with a starch-removing enzyme below 50" C. Tensile strength tests were made upon the broadcloth samples after they had been treated with 1 per cent sodium hydroxide solution, washed, dried, and conditioned. The sodium hydroxide treatment was carried out by completely submerging the cotton for 6 hours at 95" C. in a relatively large volume of the alkali.
Method I n order to prevent the formation of gelatinous masses which dissolve slowly, it is essential that the cotton sample be finely divided. Fabric disks a few millimeters in diameter, punched from various parts of the fabric, or comparable yarn lengths, are teased apart into their individual threads. Enough of these threads are taken to prepare a 0.5 per cent solution of anhydrous sample, allowing 6 per cent for the cotton moisture content. Thus in the present vork a sample of prepared, air-dry threads weighing 0.0529 gram was used because the pipet when calibrated with the 1.96 N solvent was found to deliver 9.953 ml. The charge of 1.96 N dimethyl dibenzyl ammonium hydroxide is pipetted into the dry test tube, the weighed sample of threads added, the tube carefully aligned in a clamp so that the revolving stirrer does not strike the tube walls, and the motor speeded up as much as possible without allowing air to be drawn into the solution. It is probably best to keep the temperature of the solution between 20" and 25" C. during the stirring-for example, by immersing the tubes in a water bath. Each cotton thread soon becomes the nucleus of a small individual gel particle. The dissolving samples are inspected every 15 minutes and as soon as the last gel particle has dissolved, leaving a bright, transparent solution, the stirring is stopped. The highest fluidity samples required about 0.5 hour and the lowest, about 2.5 hours for solution. After loading with the solution in the test tube, the viscometer is vertically aligned in the thermostat which is maintained a t 25" * 0.1" C. After 10 to 15 minutes several efflux times are measured, and the average time used in computing the fluidity or viscosity.
Materials SOLVEXT. The source of dimethyl dibenzyl ammonium hydroxide was the commercial product Triton F, which initially had a concentration of about 1.8 N and was concentrated to about 2 N by removing water by vacuum distillation belot6 60" C. The exact strength of the concentrate is determined by diluting a known amount with water and then titrating with 0.5 N hydrochloric acid, using methyl red as indicator. To the concentrate is now added the required amount of distilled water to bring the dimethyl dibenzyl ammonium hydroxide to a strength of 1.96 * 0.01 N . Used solvent is recovered by precipitating the cellulose by cautious acidification with a measured amount of normal sulfuric acid, and then filtering. The clear acid solution is now treated with an amount of 0.2 N barium hydroxide solution equivalent to the sulfuric acid added, in order to precipitate the sulfate ion quantitatively. After the barium sulfate has settled, small portions of the clear liquid are acidified and treated with either sulfate or barium ion. If a precipitate is obtained in either, small additions of sulfuric acid or barium hydroxide solutions are made to the main solution until the clear point is reached. After filtering off the barium sulfate on a fine paper, using mild suction, the clear dilute solution is concentrated by vacuum distillation as explained above. To &reventbumping during this operation a very slow stream of air ubbles, filtered through Ascarite, is admitted beneath the liquid surface in the distillation flask. Any slight precipitate separating during the concentration is filtered off with suction on an asbestos filter. COTTON SAMPLES.All the samples of cotton, with the exception of two, used in this work n'ere bleached and finished broadcloths (furnished through the courtesy of H. I. Huey of the Sayles Finishing Plants, Inc., Saylesville, R. I.) of three different grades (both in t,he original condition and after numerous commercial launderings), TThose cuprammonium fluidities had been determined by standard procedure ( 7 , 10, 17) in the laboratory of a large industrial chemical company. Of the two other samples (furnished through the courtesy of D. J. Campbell of E. I. du Pont de Kemours 8t Co., Inc., Xagara Falls, K. Y.) of known cuprammonium fluidity, one was a fabric and the other a yarn.
I n the present work the efflux times of the cellulose solutions covered a range of 20 to 300 seconds. The efflux time for the 1.96 AVsolvent alone varied from 7.7 to 7.9 seconds with different lots of solvent, including lots several times recovered. As in the cuprammonium method, no allowance has been made here for solvent fluidity in calculating cellulose solution fluidities. However, in computing the specific viscosities the solvent viscosity is taken into consideration. If the cellulose solution contains even a slight amount of suspended matter, a slight downward drift in successive efflux times may be observed on a given sample as solid particles settle out principally upon the lower portions of the viscometer bulb walls. However, such a n effect has been observed only in the case of certain low-fluidity cottons where the efflux times are relatively long and, therefore, the fluidities substantially unaffected by the phenomenon. If bubble films formed in the lower viscometer reservoir chamber, slightly higher efflux times were observed. The following formulas were employed: o = Cpt = p = 1.088t
0.01088t
Specific viscosity
where w C
=
7
solution 7
- p solvent solvent
viscosity in poises viscometer constant p = the density of the solution in grams per cc. t = the efflux time in seconds 7 = viscosity in centipoises f = fluidity in reciprocal poises p cuprammonium = 1.4 p Triton = 8.4 =
=
1
I 30 1
l
>
I
4 25 s!
?
j
I.
‘
I
1
20
,
I
1
25g
1
1 0 ’ u0
I
?,O
5\-+ ,1,5cQ
5I 15 .
/
1
Q
) V I) a / +IO I
5
~: 2z
+--I5
I
/
I
~
1
IO
11 E I 4
5
Figure 2 shows, in the upper curve, the relation which was found between the standard cuprammonium fluidities rind the Triton F fluidities, each of the latter multiplied by 10. It appears that, in the cuprammonium fluidity region of 4 to 25, the relation is adequately represented by a straight line whose slope is one. Although the experimental points scatter more iii the higher fluidities, i t seems clear that this curve tends to flatten out somewhat here. Table I1 allows the experimental results to be compared on a viscosity basis using the centipoise as the unit. The specific viscosities, given in the last two TThen columns, these afford ralues a fairer are plotted basis ofascomparison. the lower
curve in Figure 2, they fall very nearly on a straight line whose slope is 0.5. ! L Figure 3 portrays the nearly linear relation
~
7
5
1
TRITON
FLUIDITY X
c, 3
1
IO
crements and the fabric’s percentage deciease in tensile strength after hot-steeping in 1 per cent sodium hydroxide solution. Such steeping (11) has been found necessary if tensile strengths of chemically modified celluloses are to be really significant.
FIGURE2. FLCIDITY-VISCOSITY RELATIOSSHIPS 0 . Fluidity in reciprocal poises o, Specific viscosity n solution -
(
11
7
1
solT7ent
solvent
Discussion
TABLEI. EXPERIMENTAL RESULTS Sample State a
b
I1
I1
Iv V
a
a
Fluidity CupramTriton rnonium X 10 Reciprocal poises 3.8 10.2 15.0 24.2 7.2 14.0 17.8 28.5 22.2 28.5 24.2 32.2 5.3 25.2
Increase in Fluidity Cuprammoniurn Triton Reciprocal poises
3.3
10.0
13.1 26.7 7 0 12.9
17.0
28.0 19.5 27.8 30.5 39.4 4.8 2: 3
Relative Tensile Strength
6:4 11.2 20.4
6:7 9.8 23.4
6:8 10.6 21.3
5: 9 10.0 21.0
6:3 2.0 10.0
i:9 11.0 15.3
100 83.5 79.9 64.1 100 99.0 87.5 67.9 100 94.5 86.2 68.9
..
..
.. ..
..
..
For the viscometer used (capillary bore 1.8 mm.), C == 0.01012. All the cellulose solutions studied had a density of 1.075 * 0.002 a t 25’ C.
Results The experimental results are summarized in Tables I and 11. All samples were cotton fabrics except IV, which was in yarn form. The second column shows that the samples were examined not only in their original bleached and finished condition, a, but, in the cases of samples I to 111, also in three other states of further cellulose modification. The treatments to produce states b, e , and d 17-ere comparable for the different samples and consisted in subjecting original portions of each sample to a definite series of laundering operations a t three commercial laundries. I n Table I the third column gives the standard cuprammonium fluidities, while the fourth column ~ l i o w sthe dimethyl dibenzyl ammonium hydroxide fluidities in poises, each multiplied by ten. Each of the latter values is the average of two or more measurements. The precision of these measurements, calculated from the average deviation from the mean, averages 2.2 parts per hundred. The fifth and sixth columns indicate the increases in fluidity, by both methods, which resulted from the above-mentioned detergent treatments. I n the last column are found the comparable relative tensile strength
I n order to obtain a rapid and complete solution of cotton cellulose in dimethyl dibenzyl ammonium hydroxide i t is of primary importance that the solvent be adjusted accurately to the strength a t which it has a maximum dissolving power for the cellulose, that the cellulose sample be finely divided. and that the dissolving mixture be efficiently stirred. It was known (23) that Triton F exhibited a solubility maximum for cellulose around 2 N . From numerous preliminary experiments in which time, temperature, and stirring methods as well as solvent concentration mere varied, it was found that a Triton F concentration of 1.96 * 0.01 N is most efficient. I n contrast to cuprammonium hydroxide the Triton F solvent is stable, if ordinary precautions are taken, but its cellulose solution is somenhat affected by air. For example, a sample which showed a fluidity of 13.1 a half hour after the completion of a 2-hour dissolving period, gave a value of 13.5 after standing an additional hour, and a value of 13.8 after a further hour. A sample which showed a fluidity of 3.4 within a half hour after the completion of dissolving rose to a value of 4.5 after standing for 12 hours in the viscometer. Therefore, i t is recommended that fluidities be measured within a half hour after solution is complete. However, since results reproducible within the limits
TABLE11. Sample State I
a b C
I1
d a
b
EXPERINEXTAL
--ViscosityCuprammonium Triton Centipoises 26 9.8 6.7 4.1 14 7.1 5.6 3.5 4.5 3.5 4.1
3.1
19
4.0
306 100 76.3 37.5 144 77.5 58.: 35.l 50.3 36.0 32.4 25.4 209 39.5
RESULTS Spec-fic Viscosity Cuprarnmoniurn Triton 17
5 .SI
3.7 1.Q 8.7 4.c 2.9 1, f , 2.2 1.:,
1.9 1.2
12 1 E,
.
35.4 10.9 8.1 3.5 16.1 8.2 6.0
3.3 5.0 3.3 2.9 2.0 23.9 3.7
IXDUSTRIAL AND ENGINEERING CHEMISTR’k-
154
indicated were obtained without working in an inert atmosphere, or otherwise limiting the effect of air, this complication has not been introduced in the present method. The effect of air in increasing the fluidity of the cellulose solution, particularly during the dissolving operation, is now being studied. Because the 1.96 14’ Triton F has a fluidity of about 11.9 while the cuprammonium hydroxide solvent has a value of about 70 ($), a fairer evaluation of the relative behaviors of these two solvents is afforded by a comparison of specific fluidities or specific viscosities. From the data already considered i t is seen that the Triton specific viscosities, for all the samples studied, are twice the cuprammonium specific viscosities, within an average relative error of 8 per cent. Therefore, it appears from this comparison of solute viscosities that cotton cellulose of the types studied is dis~
5
--I
-r~
YOL. 12, KO. 3
loss in strength and fluidity determined by the cuprammonium method. Therefore, on the basis of comparison both with the cuprammonium fluidity values and with the tensile strength measurements, i t is concluded that in the case3 studied the fluidity (or viscosity) of a cotton sample in 1.96 -V Triton F solution is a sensitive quantitative measure of the degree of modification of the cellulose dissolved therein. However, until more is learned about any effects which slight variations (not directly related to basicity) in Triton F composition can have upon cellulose fluidity, it is recommended that each lot of Triton F after concentration t o 1.96 ,V be checked in its behavior with cellulose of known cuprammonium fluidity or cellulose whose extent of degradation is known. It is hoped to extend this investigation over a wider range of fluidities and to celluloses modified by other means.
Summary
-
I
I
I The
different samples of bleached cotton cellulose exaniiiied were found t’o dissolve readily in dimethyl dibenzyl ammonium hydroxide (commercially known as Triton F) to produce solutions whose fluidities (or viscosities) are a measure of the extent to which tlie cellulose has been modified. For the celluloses studied the Triton fluidities are very nearly a tenth, and the Triton specific viscosities very nearly twice the corresponding cuprammonium hydroxide values. The Triton method is simpler and more rapidly carried out than standard cuprammonium methods.
dcbnowledgment The Triton solvents used in this investigation and certain information about their properties were furnished through the courtesy of D. H. Powers of the Rohm & Haas Co. BETWEEN TRITON FLUIDITY ISCREMENTS ASD FIGURE 3. RELATIOX DECREASE IN TENSILE STREXGTH
Literature Cited
Fluidity units are reciprocal poises X 10. 0. Sample I 8 . Sample I1 6. Sample 111
(1) Am. Chem. SOC.Committee on Viscosity of Cellulose, IND. ENG.CHEY.,Anal. Ed., 1, 49-51 (1929).
solved by dimethyl dibenzyl ammonium hydroxide with less degradation than is the case with cuprammonium hydroxide solution. This is an important advantage in a method for the evaluation of modified celluloses. I n the cuprammonium fluidity region of 4 to 25 it is clear from Figure 2 that there is also a n essentially linear relation between cuprammonium solution fluidity values and Triton solution fluidity values. Furthermore, i t is evident from Table I that Triton fluidity values in reciprocal poises when multiplied by 10 give cuprammonium values in the same units within an average relative error of 9 per cent. When both fluidity methods have been more rigidly standardized still better agreement is to be anticipated. Tensile strength measurements have long been recognized as practical means of ascertaining the extent of degradation of cellulose when in yarn or woven form. If the alkali-soluble decomposition products of cellulose are first removed, tensile strength becomes a much more accurate measure of chemical modification in cellulose, providing mechanical damage is negligible. Thus proper tensile strength nieasurenients offer a n independent means, quite apart from cuprammoniuni fluidity comparisons, for evaluating the significance of the Triton fluidity values. It is clearly evident from Figure 3 that nearly linear relations exist between increase in Triton fluidity and the degree of cellulose degradation as measured by decrease in relative tensile strength. -4similar relation has been found (10) in the case of yarns (attacked by both acids and hypochlorite solutions) between per cent
( 2 ) Bingham, E. C., and Jackson, R. F., Bur. Standards, BUZZ. 14. 59-86 (1918). Birtwell, C., Clibbens, D. i., and Geake, A., J . Textile Inst., 17, 145-70T (1926).
Ibid., 19, 349-64T (1928). Birtwell, C., Clibbens, D. A , and Ridge, B. P., Ibid., 16, 13-52T (1925).
Cannon, AI. R., and Fenske, M. R., ISD. ENG.CHEM.,Anal. Ed., 10, 297-301 (1938). Clibbens, D. A , and Geake, A,, J . TmtileInst., 19,77-92T (1928). Clibbens, D. A, Geake, A , and Ridge, B. P., Ibid., 18, 2778 7 T (1927).
Clibbens, D. A . , and Little, A. H., Ibid., 27, 285-304T (1936). Clibbens, D. A , and Ridge, B. P., Ibid., 19, 3 8 9 4 0 4 T (1928). Davidson, G. F., Ibid., 29, 195-218T (1938). Fabel, K., Kunstseide, 18, 5-7 (1936). Farr, W. K., Textile Research, 7, 65 (1926). Farrow, F. D., and Neale, S. M., J . Textile Inst., 15, 157-72T (1924).
Gibson, W.H., J . Chem. SOC.,117, 479-84 (1920). Gibson, W.H., Spencer L., and McCall, R., Ibid., 117, 484-93 (1920).
Guernsey, F. H., and Horvells, L. T., Am. D g e s h f Reptr., 26, 62-7P (1937). Joyner, R. A, J . Chem. SOC.,121, 1511-25; 2395-409 (1922). Lieser, T., Ann., 528, 276-95 (1937). hlease, R. T., J . Research S a t l . Bur. Standards, 22, 271-83 (1939).
Okada, H., and Hayakawa, E., Cellulosechem., 12, 153-8 (1931). Ost, H., 2. angew. Chem., 24, 1892-6 (1911). Powers, D. H., private communication. Powers, D. H., and Bock, L. H., U. S. Patent 2,009,015 ( J u l y 2 3 , 1935).
Sheely, h1.L., ISD. EKG.C H E X , 24, 1060-4 (1932). Stamm, A. J., and Cohen, TV. E., J . Phus. Chem., 42, 921-33 (193s).
Stciner, 1,. -I., ISD. EXO.C H E x f . , -\rial. E d . , 10, 5%-4 (1938)
