INDUSTRIAL AND ENGINEERING CHEMISTRY
868
Catalytic alkylation involves reaction of the mixture of unsaturated Cd hydrocarbons with isobutane a t ordinary temperatures in the presence of very strong sulfuric acid and with vigorous agitation. Since the product is saturated, subsequent hydrogenation is unnecessary. The mixed octanes which result are nearly as high in antiknock value as those from the hot acid process, and the yields are much greater. The reaction is indicated in Figure 3. n-Butylenes Isobutylenes Isobutane
I
alkylation
isooctanes
2,2,3-trimethylpentane 2,2,4-trimcthylpentane and others +Butane FIGURE3. CHEMISTRYOF CATALYTIC ALKYLATIORT FOR IsoOCTAXE MAXUFACTORE
Still another method for synthesizing a high-octane product involves the interaction of isobutane with ethylene a t high temperatures and pressures, such as 900" F. and 5000 pounds per square inch. This process, known as thermal alkylation, gives a branched-chain paraffin containing six carbon atoms, 2,2-dimethylbutane, known as neohexane. The reactions are shown in Figure 4. The photographs show views of plants which are producing high-octane blend agents for aviation purposes.
Ethylene Isobutane PIGCRE
]
4.
thermal alkylation
Vol. 33, No. 7
.neohexane
2,2-dimethylbutane
REACTIONS I N T O L V E D I N M l N U F A C T U H E O F NEOHEXAXE
The developments described are representative of commercial organic syntheses which are coming to the fore in the oil industry under the stimulus of a demand for higher quality products. The synthetic products are expensive in comparison with natural fuels and lubricants from petroleum, b u t refiners' synthetics are relatively cheap when contrasted with synthetic chemicals as a group. The rapidity with which synthetic fuel production is developing is indicated by the fact that its annual volume already compares favorably with the production of the coal-tar industry. Since this paper is restricted to a consideration of synthetic material, i t deals with only a minor phase of the chemical and chemical engineering research of the oil industry. Within this field the industry's present advanced position is due primarily to the combination of large supplies of raw materials and an intense concentration of research and development activity. PRESENTED at t h e National Industrial Chemical Conference, National Chemical Exposition, Chicago, 111.
Behavior of Cotton Fiber With Ammonium Oxalate and Cuprammonium Solution E. HEUSER AXD J. W. GREEN The Institute of Paper Chemistry, Appleton, 15%.
CCORDING to Farr and co-workers (5, 6 ) , the cell membrane of the cotton fiber and other plants is built up of cellulose particles surrounded by a cementing material. They state that the cell wall of young and of mature fibers may be disintegrated into the two constituents by certain treatments. I n most cases the particle material was obtained by subjecting the fiber to treatment with hydrochloric acid of various concentrations. Since the cementing substance is said to consist chiefly of a noncellulosic pectic material, an aqueous ammonium oxalate solution, usually applied for removing pectin from plant material, is regarded as being most suitable for removing the bulk of the cementing substance from the cotton fiber (3). Simultaneously, provided the treatment is long enough, the fibers are said to disintegrate into particles. Thus, continuous treatment of raw cotton with a 2 per cent aqueous ammonium oxalate solution for 3126 hours (about 130 days) a t 75" C. (4) supplied F u r with sufficient material of both particles and cementing material for further studies. In evaluating these results, the interpretation of which is rather unusual from the viewpoint of the cellulose chemist, i t appears desirable to distinguish between the two types of treatment under which disintegration of the fibrous material into cellulose particles was observed. For example, under the action of strong hydrochloric acid for 18 hours a t
A
room temperature or of more dilute acid for a longer period disintegration of the fiber probably does take place. Such treatments lead to hydrocellulose, a cellulosic material which has lost its fibrous structure and appears in the form of fiber fragments. Farr claims without evidence other than stain and optical tests ( 3 , 6 )that the particles show no signs of degradation. But proof that the latter does occur is, without doubt, derived from the molecular weight of the particle material; this was determined by the ultracentrifugal method to be only about 40,000 (8). This value is less than one twelfth of that usually found for raw cotton which Farr used as a source for the isolation of the particles. It appeared improbable, then, that treatment with such a neutral agent as ammonium oxalate should lead to the same result, unless the assumption was made that, under the conditions applied, oxidizing and hydrolyzing effects would be exerted. T o reduce the possibility of an oxidizing effect, Farr's experiments were repeated in the absence of air-i. e., in an atmosphere of nitrogen, carefully controlled for the duration of the treatments. For comparison some treatments were also carried out in air. The cellulosic material was raw cotton lint. It was first extracted with alcohol and benzene in order to remove the wax, so that the extracted material would wet easily with the
July, 1941
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
aqueous agent; 0.5 and 2 per cent ammonium oxalate solutions were used. According to Farr so much of the cementing material ought to have been removed under these conditions that the fibers would have disintegrated into particles. However, the samples showed no signs of disintegration whatever after treatment with either oxalate solution. In addition, the raw cotton material was subjected to six 24-hour extractions with 0.5 per cent ammonium oxalate solution. When concentrated and acidified with alcoholic hydrochloric acid, the last two filtrates gave only slight precipitations, which indicated that almost all of the peptic material had been removed. The residue of the repeated extraction showed no signs of disintegration. No signs of disintegration could be observed after the pectin-free material was again treated with 0.5 per cent ammonium oxalate solution a t 70-80' C. a t intervals for 600 hours (25 days), 1200 hours (50 days), and 2064 hours (86 days) in air. Nor was there any change after cotton fibers, which had been extracted with benzene and alcohol only, were subjected t o treatment with 0.5 per cent ammonium oxalate solution a t 70-80" C. for a total time of 2040 hours (85 days) in air, and with 2 per cent ammonium oxalate solution a t the same tbmperature for a total time of 2640 hours (110 days) in the nitrogen atmosphere. No explanation can be given for the discrepancy between these results and those reported by Farr. She gives no details of experimental treatment. Although the source of the cotton material was different in the two cases, it is difficult to imagine any difference great enough to account for such a divergency of results.
Cellulosic Dispersions Farr and co-workers (2) also claimed that, on treatment of cotton fibers with cuprammonium solution such as that commonly used for ascertaining the solution viscosity of cellulosic materials, it is merely the cementing substance which goes into solution and causes the viscosity to increase; according to them, the cellulose particles remain undissolved and are thus not responsible for the increase in viscosity of the cuprammonium solution. These conclusions are incompatible with the view commonly held by cellulose chemists. It is known that a good dispersion of cellulosic material in cuprammonium solution depends upon many factors, and that if one or the other of the essential factors is neglected, dispersion may not occur at all. To avoid such influences, it was thought desirable t o prepare dispersions of cellulosic materials in cuprammonium hydroxide under such conditions as would make it probable that the ultimate degree of dispersion had been reached; moreover, from the viscosity measurements of the solutions, the degrees of polymerization (D. P.) and molecular weights could be calculated. No substantial change in the degree of polymerization of the cotton fibers which had been treated with ammonium oxalate solution would be in agreement with the observation that no disintegration of the fibers had occurred. The apparatus for determining the specific viscosities according to Staudinger's method was a modification of that used by Lottermoser and Wultsch (9). The dissolver and viscometer were separate pieces of apparatus, so designed that samples of the solution could be easily taken from time to time to test for complete solution (i. e., maximum viscosity). The nitrogen was purified over hot copper gauze in accordance with a suggestion made by Kendall (7). AI1 determinations were made in a water bath a t 20 * 0.02" C. The dissolver was kept in the bath during the period required for solution of the sample. All operations were shielded from the light whenever possible. Each figure in the subsequent
869
tables pertaining to the viscosity data refers to a separate solution obtained from a different sample of cellulosic material. The maximum error allowed in duplicate determinations was 5 per cent. The cuprammonium solution was prepared in accordance with the description given by Lottermoser and Wultsch. Although commercial cellulose samples will usually dissolve in such a cuprammonium solution within 15-16 hours, the raw cotton material used in this investigation requires 100 to 120 hours t o dissolve completely. The very dilute solutions (0.01 per cent) were obtained without stirring. The possibility of making a mistake by not waiting long enough is indicated in Table I. The maximum viscosity was regarded as the best value.
Effect of Ammonium Oxalate Solutions RESULTSWITH 0.5 PER CENT SOLUTION.According t o Farr and co-workers, raw cotton fiber freed of its cementing material should cause no increase in viscosity over that of the cuprammonium solution itself. However, both the material treated for over 3000 hours with 0.5 per cent ammonium oxalate solution and that subjected to repeated extraction with the same agent (Table 11, A ) show the high viscosities which would be expected on the assumption that the cellulosic materials are thoroughly dispersed in the cuprammonium solution. Table I1 also shows that, in spite of the nitrogen atmosphere, the cotton fiber had suffered some degradation; the molecular weight of the sample treated for 3000 hours (405,000 on an average) was 17 per cent lower than that of the original sample (488,000). The molecular weight of the repeatedly extracted sample (440,000 on an average) lies between the two others, which indicates that on repeated extraction, during which no precautions for excluding the air were taken, little degradation of the fiber has taken place (about 10 per cent) but not so much as on the 130-day treatment. TABLEI. INCREASE IN OBSERVED DEGREEOF POLYMERIZATION (MOLECULAR WEIGHT) OF COTTON LINTWITH TIMEOF SOLUTIOS~ Hours of
Contact withCuam 20
9sp. co 9/c Mol. W t . D. P. 0.0733 0.000655 112 224,000 1382 48 0.0928 0.000516 183 366,000 2260 214 428,000 2640 96 0.163 0.000763 120 0.1043 0.000428 244 488,000 3000 168 0.156 0.000643 243 486,000 3000 a Cuam is cuprammonium solution. np. is specific viscosity. T h e concentration term cg is given as grams per liter, divided b y 162, t h e molecular unit of cellulose. All weights are on t h e oven-dry basis. T h u s 0.0810 p m per liter would be e uivalent to a cg yalue of 0.00050. Actuahy each issolver held a volume 250 cc. of solution a n d 25-40 m8. samoles were weighed. T h e molecular weight is calculated from t h e qsp f i gvalies, using Staudinger's K m constant of 5 X 10-4 ( 2 8 ) . D. P. is degree of polymerization-i. e., molecular weight divided b y 162.
08
The result obtained in the nitrogen atmosphere seems to indicate that it had not been possible to exclude the air entirely. This conclusion is supported by results of parallel experiments in air. Samples were taken after 38, 54, and 85 days. I n contrast t o the untreated raw cotton material and the repeatedly extracted fiber, samples which had been treated for a long time needed only 72-hour contact with the cuprammonium solution to ensure ultimate dispersion. The results are presented in Table IIB. I n this case the reduction of the molecular weight amounted to 25 per cent after a total of 2040 hours of treatment. This result and some data obtained from treatments with the 2 per cent solution show that the air is a t least partly responsible for the degradation which takes place during the treatment.
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Vol, 33, No. 7
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE11. MOLECULAR WEIGHTSOF COTTONLINT BEFORE ASD AFTER TREATMENT WITH 0.5 PERCENTAMMONIUM OXALATE SOLUTIOXS Hours of Contact with Treatment of Lint Cuam vsg. Extd. with alcohol 120 0.1043 and benzene 168 0.166 A.
244 243
486,000
3000
In Nitrogen Atmosphere
Treated with 0.5% s o h for 3000 hr. at70-80" C . Repeatedlyextd. with 0.5% soln. (pectinfree)
144 144 144
0.1426 0.1436 0.1207
120
0.113 0.110
Treated with 0 . 5 R soln. for 912 hr.
72 90 72
0.116 0,127 0.181
Same after 1296 hr.
72 72
Same after 2040 hr.
72 72
168 120
Mol. Wt. D. P. 488,000 3000
q/c
cg
0.000425 0.000643 0.000705 0.000705 0.000600
202.5 204 201
405,000 408,000 402,000
2500 2520 2480
0.000507
223 217 221
446,000 434,000 442,000
2750 2680 2726
0.000585 0.000645 0.000765
198 197 197
396,000 394,000 394,000
2440 2430 2430
0 141 0 108
0 000717 0 000562
197 192
394,000 384.000
2440 2370
0.125 0.125
0 000686 0.000702
182.5 183
365,000 366,000
2260 2260
0.117
B.
0.000507 0.000529
I n Air
Nevertheless, the reduction of the molecular weight by about 25 per cent is much too small to cause any disintegration of the original fiber into fragments which would be similar to those obtainable under the influence of hydrochloric acid where the chain length is decreased by a t least 90 per cent. The results obtained with the pectin-free material after treatment with 0.5 per cent ammonium oxalate solution in air are similar to those obtained with the unextracted material (Table 111). TABLE111. MOLECULARWEIGHTSOF PECTIN-FREE COTTON LIXTAFTER TREATMENT WITH 0.5 PERCENTAMMONIUM OXALATE SOLUTION I N AIR AT 70-80" c. Hours of Hours Contact of Treat- with ment Cnam
qsp.
CO
r)/c
80 80 120
0.123 0.1303 0.1275
0.000603 0.000660 0.000660
204 197.5 193.5
1200
120 50
0.132 0.095
0.000714 0.000503
2064
120 120
0.118 0.134
0.000688 0.000778
600
Mol. Wt. 408,000
D.P.
395,000 387,000
2520 2440 2430
185 189
370,000 378,000
2280 2330
171 171.5
342,000 343,000
2110 2120
The reduction of chain length here amounts to 22.3 per cent compared with the samples repeatedly extracted but not further treated, and to 30 per cent compared with the original cotton lint. Again this reduction is not sufficient to disintegrate the fiber into particles. RESULTS WITH 2 PER CENT SOLUTION. The same conclusion may be drawn from the results of experiments in which the cotton lint (extracted with benzene and alcohol only) was treated with 2 per cent ammonium oxalate solution in the nitrogen atmosphere for 2640 hours (110 days) a t 70-80" C. I n these experiments the original technique of treatment in the nitrogen atmosphere was improved. The equipment is described later. I n addition, great care was taken in freeing the distilled water, as well as the nitrogen used, of oxygen. Three dispersions in cuprammonium were prepared. The results are given in Table IV. I n spite of the stronger ammonium oxalate solution, the reduction in chain length (12 per cent) amounted to less than when the concentration of the reagent was only 0.5 per cent (17 per cent, Table 11, A ) ; this result is due to the effect of the improved technique of reducing the air present in the system.
The data are illustrated in Figure 1. Instead of molecular weights, the v / c values (specific viscosity over concentration) are plottcd against time of treatment with the pectin-removing agent. The curves show the gradual degradation of the cellulosic material with time of treatment and the lesser degradation in nitrogen (curves I and 11) as compared with air (curves I11 and IV). The improvement in the elimination of air is also seen when comparing curves I and 11. Since it is difficult to remove all oxygen from the system (11) the degradation effect as shown in curve I may still be due to the presence of traces of oxygen. On the other hand, the effect may in part be due to hydrolysis which could occur under the influence of the aqueous solution a t elevated temperature and for a relatively long time, considering the fact that the p H of the aqueous agents was between 6 and 7 . This was the same as that of the distilled water with which the ammonium oxalate solutions were prepared. TABLEIS7. MOLECULARWEIGHTSOF COTTONLINT AFTER TREATMENT WITH 2 P E R C E N T AMMONIUM OXALSTE SOLUTION IN THE XITROGEN ATMOSPHERE Hours of Contact with Cuam
qnp.
72 80 80
0.142 0.166 0.144
CL7
0 000635 0,000772 0 000682
q/c
Mol. W t .
D. P.
217 215 211
434,000 430,000 422,000
2680 2660 2610
Interpretation of Results
Xeither on the removal of pectin from the raw cotton fiber nor on the treatment of the pectin-free fiber with the same pectin-removing agent does any disintegration into smeller fiber elements take place. Hence, the pectin does not seem to contribute to the continuity of the structure of the raw cotton fiber. The fact that no disintegration takes place when the pectin-free fiber is treated with an agent supposed to remove the bulk of the cementing material seems to indicate that no other material is removed which would be essential in maintaining structural continuity. Thus i t would appear that the so-called cementing material is nothing but pectin and that the existence of a cementing material as a constituent of the cellulose fiber with the function of holding the cellulose particles together is problematical. This interpretation is in agreement with the conclusions which Kickerson and Leape (10) have drawn from experiments in which raw cotton fiber was extracted with am-
I
I
50
103
150
I
DAYS
FIGURE 1. DEGRADATION OF RAW COTTONIN AMMONIUM OXALAT~E SOLUTION AT 70-80" C. I. 11. 111. IV.
2% oxalate solution and nitrogen atmoaphere 0.5 oxalate solut?on and nitrogen atmosphere
0.5p oxalate solution and air Pectin-free cotton in 0.5% oxalate solution and air
July, 1941
INDUSTRIAL AND ENGINEERING CHEMISTRY
monium oxalate solutions and various other agents. This interpretation also appears t o be in good agreement with the view held by Bailey and Kerr (1) which is based upon microscopical evidence. The presence or absence of pectin has no influence upon the viscosity of the cotton fiber in cuprammonium solution. Thus it appears that, if the fiber is thoroughly dispersed, the viscosity is a property of the cellulosic substance and not of the material which may be extracted from the fiber. This conclusion is in agreement with that recently published by Harris and co-workers (18). The drop in molecular weight occurring on treatment with ammonium oxalate solution is probably due to oxidizing and hydrolyzing effects rather than to the removal of pectin.
FL
-
E x p e r i m e n t a l Conditions I n all experiments the starting material was raw lint from so-called Upland cotton (Mexican variety) grown at Statesd e , N. C., in 1938 and obtained through the courtesy of Thomas Kerr of North Carolina State College. The material was cut by hand into pieces of about 2-3 mm. The cut material was stirred in water to ensure uniform mixing, filtered, and air-dried. The extraction was carried out first by immersing the sample in alcohol for 16-hour intervals, followed by extraction with a 50-50 per cent mixture of alcohol and benzene in the same manner. For the treatment with the ammonium oxalate solution, the oil bath was kept within the temperature range 70-80' C. by adjustment of a gas flame. The p H of all aqueous solutions ranged from 6 to 7, and this same range was observed after the conclusion of the experiments. No buffering was attempted. I n each of the experiments exposed to the air, the fibers (20 grams) were simply immersed in the oxalate solution (500-600 cc.) in an Erlenmeyer flask; a beaker inverted over the mouth of the flask prevented excessive evaporation of water. The flasks were weighed a t intervals, and any water lost was replaced. Samples were easily removed from such a system. About 1.00 gram was taken each time, thoroughly washed, iecut by hand, thoroughly stirred in water, and filtered to allow homogeneous sampling. With the nitrogen atmosphere, obviously no samples could be taken a t intervals. The first of these experiments was carried out with 20 grams of lint and 540 cc. of 0.5 per cent oxalate solution in a liter Erlenmeyer flask. The lint was first placed in the dry flask, and the neck was sealed to a length of 10-mm. tubing which served as an air condenser. To this tube was attacked a T-tube through which the flask was evacuated and flushed with ordinary tank nitrogen. The oxalate solution (prepared with water distilled in a stream of nitrogen) was added and the flask placed in the oil bath. The air condenser was attached to a large bottle containing nitrogen and connected t o the air with a fine capillary. I n this way diffusion of air was very slow and yet no pressure developed in the flask. The experiment with the 2 per cent ammonium oxalate solution in nitrogen was carried out with improved technique. The nitrogen was purified over hot copper gauze. The water was distilled over manganese hydroxide in a stream of nitrogen in an all-glass apparatus. The cellulose (1gram) was placed in a glass tube, 100 X 35 mm., with a 10mm. tube sealed t o it. After thorough flushing with nitrogen, the solution was introduced and the end of the 10-mm. tube was sealed off. The container was then kept in the water bath until the necessary time had elapsed. I n all the foregoing procedures, including the making up of the oxalate solution, air was rigorously excluded through the use of Ttubes and tight rubber connections. All glass seals were tested with the usual Tesla coil for pinholes.
871
c DH
VAC.
al & NITR OGEN
FIQURE 2. APPARATUS FOR DETERMINATION OF MOLECULAR WEIQHT Upper left, flusher; below dissolver. upper right, visoometer; oenter: ouprammbnium bottle
right
Determination of Molecular Weight APPARATUS. The flusher (Figure 2) is a permanently mounted rtp aratus consisting of a nitrogen purifier, FC, and a three-way varve, Q, for alternate evacuation and flushing with nitrogen. The nitrogen pressure is relieved throu h bubbler FB and maintained by closing inch clamp F A . #E is an overflow trap t o catch any liquid (%utylphthalate) which might rise too far in the bubbler tube when nitrogen is bled into an evacuated system.
872
INDUSTRIAL AND ENGINEERING CHEMISTRY
The purifier is a roll of copper gauze, heated b a Nichrome wire on a quartz rod (7). The maximum gas l o w over this gauze is 500 cc. per minute. The reservoir bulb below valve Q serves to slow down this flow into the evacuated system. When the top quarter of the copper becomes blackened, the gauze is reduced with hydrogen. The dissolver consists of a 250-cc. volumetric flask, D A a 100-cc. mixing chamber, DB, and a sintered glass filter, hC. The sample is weighed into D A . A large Bunsen clamp, fastened to the flusher backboard, supports the dissolver at DB. The three-way valves, D E and DF, have T-bores; their adjustments will be described later; for example, D E 23 and DF 23 are shown in the larger sketch of the valves at the lower right. The viscometer has a capillary of 0.4-mm. diameter and 12-cm. length. Bulb V D has a volume of 3 cc. Overflow basin V E provides a constant head. The apparatus is clamped in a support at the two bulbs V D and V K so that they are in a vertical line. A circular level on the support is provided to reproduce the same position. The time of flow for the cuprammonium solution at 20" C. was about 300 seconds. The cuprammonium solution is repared according t o the from copper hydroxide. Lottermoser and Wultsch method The resulting solution is stored under nitrogen in refrigerator a t 10" C. in a brown 2-liter bottle with a ground joint having two valves, CK and CL. PROCEDURE. The dissolver, with the sample in D A , is connected to the flusher from FH to DH and t o the cuprammonium bottle from F L to C L ; joints DI and CK are connected by an intermediate piece of heavy rubber tubing with the appropriate &&ts at each end. A bubbler with valve B J i s attached to joint
6)
DJ.
With DG closed and D E adjusted to position 23 and DF to 12, the bubbler liquid is sucked up (by vacuum through &) t o just below valve BJ which is then dosed. The system is then flushed five times with nitrogen, BJ is opened, and nitrogen is bubbled through for 30 seconds. The liquid is again sucked up to BJ and the process repeated. B J is then closed, DG and DD are opened, and the system is flushed ten times. Each flushing takes approximately one minute. BJ is opened, clamp F A closed, D E adjusted to position 13 and DF to 123, C L opened, and CK then opened. The solution is forced up through CK and D D into flask D A . As soon as sufficient pressure is reached in the bottle, C L is closed and P A opened. Valve DD is closed when the 250-cc. mark is reached. CL is opened to relieve pressure in the bottle. Joint DI is broken and the cuprammonium solution in the rubber tubing allowed to flow back to just below valve CK. Joint CK is then broken and the bottle returned to the refrigerator. Valve DG is closed, DE and DF are adjusted to position 13, the bubbler is removed, and D J is capped. Flask D A is shielded from the light with a piece of black cloth. The dissolver is then supported in the water bath at 20" C. with a clamp at DB. After the requisite time for solution of the sample (1 to 7 days), the dissolver is again connected t o the flusher. The rubber tubing leading to F L is clamped shut. The system from Q to D E is flushed ten times, and with a slight nitrogen pressure D E is changed to 23; then valve DF is quickly shifted from position 13 t o 123 to 12 (not from 13 t o 23 to 12). This should allow no diffusion of air from arm 2 to arm 3 of valve DF. The viscometer, with all valves open, is attached through DJ and VJ. The bubbler is attached to V B with a,piece of rubber tubing, liquid is sucked up to BJ, the viscometer 1s flushed five times, nitrogen is bubbled through BJ for 30 seconds, and the process is repeated. With B J open, F A is closed, DG is opened, and D E and DF are adjusted to positions 23 and 13. The cuprammonium solution is forced up into mixing chamber DB. Before it reaches the top, D E is turned to position 123, and the liquid falls back into D A . This mixing is done ten times, then the solution is forced over through DC into the viscometer. B E is half-filled, the solution in DB is run back into D A , DG is closed, and DF and D E are adjusted to positions 12 and 23. V C is then closed and the solution in bulb V K forced up into V D and into the reservoir above. F A is opened, V A closed, V C opened momentarily to relieve pressure, and V B closed. The viscometer is disconnected from D J and B J , tilted to fill V K from V E , and then ut into the support in the water bath. After 10-15 minutes f C is opened and the time of flow between the marks on V D noted. The viscometer and dissolver are cleaned with 6 N sulfuric acid, water, and acetone. The valves should be lubricated frequently, as the acetone produces channeling. With practice the dissolving operation can be carried out in less than an hour. Thirty minutes are required to mix the resulting solution and fill the viscometer. The mixing and
Vol. 33, No. 7
filling of the viscometer are carried out with the exclusion of light. A black cloth bag with three zippers is fitted over the dissolver and viscometer, and allows satisfactory operation. In the present work three dissolvers and one viscometer were used. A possible improvement would consist in lacing filter DC on the viscometer below valve V A . This w o u l ~also reduce the cost of the dissolvers.
Summary 1. Raw cotton lint, freed of wax, etc., by extraction with alcohol and benzene was kept in contact with 0.5 and 2.0 per cent ammonium oxalate solutions in the air and in a nitrogen atmosphere a t 70-80" C. for 600-3000 hours. The other samples were extracted with 0.5 per cent ammonium oxalate solution during six 24-hour periods. The pectin-free material obtained was again kept in contact with 0.5 per cent ammonium oxalate solution at 70-80" C. in air for 2000 hours. I n all cases the fibers emerged from the treatment physically undamaged. 2. The original wax-extracted cotton material as xell as the various preparations resulting from the treatments with ammonium oxalate solution were dissolved a t very low concentrations in cuprammonium solution and the specific viscosities ascertained. From the viscosity data the molrcular weights (degrees of polymerization) were calculated according to Staudinger's conversion equation. 3. The viscosities were found to increase with time of contact between samples and cuprammonium solution until a maximum viscosity was reached. 4. The original cotton fiber yielded a molecular weight of about 488,000. 5. The molecular weights of the samples treated with the ammonium oxalate solutions in air were about 25 per cent lower than that of the original material, whereas the treatment in nitrogen diminished this reduction to 17 and 12 per cent. 6. The p H of 6-7 prevailing throughout the treatments would indicate that, besides the possibility of oxidation, hydrolysis may be responsible for the degradation observed. 7 . These results show that, under the conditions applied, no disintegration of the cotton fiber into particles takes place, the raw cotton fiber as well as the pectin-free fiber dissolves in cuprammonium, and the relatively slight reduction of the molecular weight observed after treatment with ammonium oxalate solution is due to oxidation and hydrolysis. 8. The conclusions may be drawn that the existence of Farr's cementing material as a fundamental constituent of the cotton fiber is rather improbable, and that the viscosity of a solution of the cotton fiber is a property of the entire fiber and not of a problematical cementing material alone.
Literature Cited (1) (2)
Bailey and Kerr, J . Arnold Arboretum, 16, 273 (1936); 18, 261 ENG.CREM.,30, 40 (1938). (1937); Bailey, IND. Farr, Contrib. Boyce Thompson Inst., 10, 71 (1938); Compton, Ibid., 10, 57 (1938); Sisson, Ibid., 10, 113 (1938).
Farr, Ibid., 10, 77 (1938). Table I, fifth sample (1938). (6) Farr and Eckerson, Ibid., 6, 189 (1934); Farr, J. Phys. Chem., 42, 1113 (1938) : see also Barrows, Contrib. Boyce Thompson Inst., 11, 61 (1940); and Mauersberger. Rayon Textile (3)
(4) Ibid., 10, 80,
Monthly, 21, 413 (1940). (6) Farr and Eokerson, Cmtrib. Boyce Thompson Inst., 6, 311 (1934); Farr and Sisson, Ibid., 6, 315 (1934). (7) Kendall, Science, 73, 394 (1931). (8) Kraemer, IND.ENQ.CHEM.,30, 1201 (1938). (9) Lottermoser and Wultsch, Kolloid-Z., 83, 194 (1938). (10) Nickerson and Leape, IWD.ENQ.CHEM.,33, 83 (1941). (11) Scheller. Melliand Teztilber., 16, 787 (1935). (12) Staudinger and Mohr, Ber., 70, 2296, 2309 (1937). (13) Whistler, Martin, and Harris, J. Teztile Research, 10, 269 (1940); Hock and Harris, Ibid., 10, 323 (1940).
