Unit Cell of Cellulose in Cotton Stalks and Cusps J. P. SANDERS AND F. K. CAMERON, University of North Carolina, Chapel Hill, N. C.
I
N T H I S laboratory, a study is being made of the proper-
Four series of acetates were preared above 65" C. from total celluose and mercerized cellulose, and below 65" C. f r o m t h e s a m e . Those above 65" C., described by Barnett (1) as t r i a c e t a t e , were made by a modification of the procedure of Irvine and Hirst (19) using s u l f u r i c acid i n s t e a d of chlorine and sulfur dioxide. Ten grams of dry cellulose are stirred into 50 grams of glacial acetic acid [Baker's 99.5 per cent (CHZCO)~?] containine 0 . 5 to 1.O gram sulfuric acid, anduallowed t o k a n d for 30 minutes a t room temperature. The mixture is then heated to slightly above 65" C. and allowed to stand for about an hour until the cellulose is completely transformed to a viscous liquid. Cooled t o 30" C., an equal volume of chloroform is added, then a relatively large volume of water. The chloroform is volatilized by heating, and the granular precipitate is washed free from acid and dried. ACETATE BELOW 65" C. The same procedure was used except that the temperature was never raised much above that of the room, a much longer time was required for the formation of the viscous solution of the acetate, and chloroform was not added for precipitation. HYDRATED CELLULOSE.Preparation was according to Snell (30). Thirty-seven grams of alpha-cellulose were immersed in 558 ml. of 17.5 per cent sodium hydroxide solution for 1.5 hours a t 20" C. Filtered, the residue was compressed to about onethird its volume, picked to pieces, and stored in a closed bottle for 48 hours or longer a t 18" C. When "ripe', it was mixed with carbon disulfide together with 120 d.of a 4 per cent sodium hydroxide solution and 25 ml. of a 10 per cent sodium sulfite solution. Standing in a closed bottle a t 18" C., a precipitate appeared in several days and was completed in 2 to 3 weeks. The precipitate, after filtration, was washed. REGENERATED CELLULOSE.Chardonnet silk or regenerated cellulose was prepared from total cellulose and from mercerized cellulose. The pulp was immersed in a mixture of 44 per cent sulfuric acid, 38 per cent nitric acid, and 18 per cent water; it was kept at 40" C. until, after pressing and washing, it was completely soluble in a mixture of 60 per cent alcohol and 40 per cent ether. The immersion in the acid bath requires from 30 minutes to 2 hours. The nitrocellulose was washed first with cold then with hot water after several hours of contact with the latter. It was denitrated by 3-hour contact with ammonium sulfide solution at room temperature, washed free of sulfur products, and dried. KITROCELLULOSES. These were prepared from total cellulose and mercerized cellulose as above described, omitting the denitration with ammonium sulfide.
The cellulose of cotton stalk a n d cotton cusps is shown to be the same cellulosefound in cotton lint, spruce, pine, and poplar. T h e unit cell or fundamontal structure obtained by a chemical treatment is the same irrespective of the origin of the cellulose. Differences in physical properties of products f r o m celluloses of diflerent origins are to be sought in micelle or Jibroid structures. These are being investigated.
ties of whole cotton-i. e., lint, s t a 1k s , and cusps-with a view t o its p o s s i b l e value a s a s o u r c e of c e l l u l o s e . A g a i n s t this p o s s i b l e value, manufacturers of cellulose products have objected that it is well known t h a t the c e l l u l o s e of c o t t o n stalk and CUSD is not chemically the same substance as the cellulose of lint or of spruce wood, and t h a t it will not yield the same products when treated with chemical reagents. Although no authoritative support has been found for this view, it has become necessary to investigate it. The chemical composition of the celluloses of the several origins is identical. Comparison of the unit cells is described in this paper. A further study of micelle or fibroid structure will be reported later. The x-ray equipment is the standard assembly of the General Electric Company. A Coolidge tube with molybdenum targei, operating at 30,000 volts, gives rays of wave length 0.712 A. The cellulose sample, moistened with a little dilute solution of glue, is compacted into a flat pellet, mounted on adhesive paper, and fastened in the path of the rays coming from a slit of 0.0508 x 1.27 cm. cross section. The diffracted rays pass through a zirconia flter and are recorded on a film 4.76 x 40.6 cm. placed in circular arc of radius 20.3 cm., the sample being at the center. Exposure was 10 hours.
MATERIALS STUDIED With the cellulose obtained from stalk and cusp, respectively, was compared that from lint, and three commercial pulps-a sulfite piilp from spruce, a soda pulp from poplar, and a sulfate pulp from pine.
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Samples of stalk, cusp, and lint were pulped after cutting and grinding the first two to lengths of 0.5 cm. or less. They were seeped for 30 minutes in a boiling aqueous solution of one per cent sodium hydroxide, using 30 cc. of solution per gram of sample. The black solution resulting was removed with suction filter and the residue washed. The treatment was repeated. The residues from the second treatment were again macerated for bleaching. A calculated amount of sodium hypochlorite was added to a suspension of the pulp at 35" C. After 5 minutes of DISCUSSION OF OBSERVATIONS contact the ulp was washed on a suction filter and boiled for 15 For any particular substance, cellulose or derivative, minutes wit1 a 2 per cent solution of sodium sulfite. Washed free of sulfites, the bleaching was repeated. Lint required but practically the same spectograph was obtained, irrespective one treatment; cusps and stalks, three and occasionally four of the origin. In so far as the unit cell is a c e r n e d , the treatments to obt,ain a pure white product. The samples thus prepared, together with the commercial samples, were designated cellulose of the cotton stalk and the cotton cusps is identical with the cellulose of lint, spruce, poplar, and pine. Measure"total cellulose." ments of interplanar distances for any particular product MERCERIZED CELLULOSE. This material was prepared from the several origins varied only by 0.03 or 0.04 A., too by a method described by Ritter ( 2 7 ) . small a difference t o have any significance for the present To a 3-gram sample of total cellulose in a 250-ml. beaker are added 35 ml. of a 17.5 per cent solution of sodium hydroxide at purpose. Interplanar distances and intensities are shown 20" C. Let stand 5 minutes. Then at 2.5-minute intervals, add, in Table I. These results are in harmony with those of previous inwith continuous stirring, four consecutive portions (10 ml. each) of the sodium hydroxide solution, and let stand for 30 minutes vestigations. Levinstein (24) found the same structure for at 20" C. Add 75 ml. of water at 20" C. with stirring; separate and wash the pulp on a suction filter. Add 4 ml. of 10 per cent cellulose from cotton, ramie, and wood, as did Herzog and acetic acid to the pulp. After 5 minutes again wash and dry the Jancke (9-11) who found that it belongs to the rhombic system. Clark ( 2 ) found typical cellulose patterns in fibers PdP. 1371
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TABLEI. INTERPLANAR DISTANCES AND INTENSITIES IN SPECTROGRAPHS OF CELLCLOSE AND PRODUCTS FROM COTTON STALKSAND CUSPS Total cellulose.. ...................... . A.I n 6 M. 0 1 5hl. 3 9 4 M. 3 9 3 .S9 4 2 .S6 0 2w. 1 5 2 W. 0 0 .* .. .. .. Mercerized cellulose ......................... A. 4.40 4.00 3.14 2.58 2.44 2.18 2.00 1.86 1.69 I VS vs w M M W w vw vw Acetate from total cellulose, above 65’ C A. 8.44 6.52 5.20 4.76 4.10 3.82 3.30 2.57 .. I M M S S M hl. W W .. Acetate from mercerized cellulose, above 65’ C. A. 8.41 6.52 5.19 4.72 4.07 3.79 3.30 2.54 .. I M lf S S M M W W .. Acetate from mercerized cellulose, below 65’ C. A. 6.50 5.01 3.86 .. .. .. .. .. .. I M 5 S .. .. .. Hydrated cellulose.. ........................ A. 4.43 4.04 3.13 2.47 2.20 1:98 1:86 1:68 .. I vs vs W M M w vw w .. . . . . Regenerated from total cellulose A. 4.40 4.01 3.14 2.58 2.20 2.00 1.68 .. I vs vs W M M W vw ., .. Regenerated from mercerized cellulose.. . . . . . . . A. 4.40 4.02 3.13 2.59 2.22 2.00 1.69 .. I vs vs w M M W vw ..... . Nitrocellulose from total cellulose A. 6.49 3.95 3.30 2.54 .. .. .. .. I lt S M W .. .. .. .. Nitrocellulose from mercerized cellulose.. ...... A. 6.50 3.90 3.29 2.58 .. .. .. .. I M S M W .. .. .. .... .. a
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intensity; VS, very strong; S, strong; M, medium; W, weak; VW, very weak.
of yellow poplar, redwood, white ash, and southern pine, tates and nitrates are amorphous but in particular instances while Khouvine, Campetier, and Sutra (25) found cultures of are crystalline. This seems to be the view of Herzog (6). Acetobackr xylinum in glycerol, sorbitol, and alpha-gluohepti- However, according to Davey (S), “all cellulose compounds to1 produced membranes giving x-ray patterns identical with except the diacetate (rayon) are cryst@line.” that of cotton lint. With the exception of line 2.58 A. all the lines of the Mercerization with 17.5 per cent sodium hydroxide pro- mercerized cellulose pattern appear in the pattern for hyduces important changes. Some lines disappear, some re- drated cellulose. Hess (1Q-fs) observed that cellulose remain but with changed intensities, and new lines appear. generated from cuprammonium solutions had the same strucThe concentration of the mercerizing solution is of importance. ture as the original cotton. But Herzog (4, 8) found differSponsler and Dore ( S I ) , studying ramie, thought 13 per cent ent patterns for hydrated and natural cellulose, and atsodium hydroxide a critical solution. At lower concentra- tributed this fact to a distorted structure of the former; tions no change was produced in the x-ray patterns, but solu- and Sakurada and Hutino (28) found that alkali cellulose tions from 13 to 28 per cent produced an identical pattern, from bleached ramie fibers treated under tension with carirrespective of the exact concentration, but different from the bon disulfide gave a pattern differing from that of natural or pattern shown by products treated with solutions below the mercerized cellulose. Regenerated cellulose or Chardonnet critical concentration. Treatment with solutions near the silk showed well-defined lines in all cases, practically identical critical concentration resulted in lines from both groups. Tith those for mercerized cellulose, except lines 2.44 and 1.86 Katz (ZO), Katz and Vieweg (22), Vieweg (37), and Herzog A. belonging to the latter. But Hess and Trogus (f7)found and Londberg (5-7, f2) found that treatment with sodium that nitrated cellulose (13.5 per cent nitrogen), denitrated hydroxide brought out new lines and changed intensities of with ammonium sulfide, gives only moderately strong lines persisting lines, intensity increasing with concentration of and appears to be amorphous. No well-defined lines were alkali in the mercerizing solution. Katz and Mark (21) obtained with any of the nitrocelluloses, and accurate measfound restoration of old lines by washing out the alkali, but urements were scarcely possible. Two of the four lines obnew lines persisted. Clark ( 2 ) observed that, after removing served seemed to be common to the patterns for regenerated, the alkali from cellulose treated with 12 per cent solutions, mercerized cotton and total cellulose. They may be due t o x-ray patterns were changed permanently but not chain incomplete nitration, but the significance of the other lines is directions. Hess and Trogus (18)found a different pattern not apparent. Meyer and Mark (25) and Herzog and for products treated with concentrations above 21 per cent NBray-Szab6 (IS) found the pattern to be dependent on the from that obtained when solutions below 19 per cent were degree of nitration. Trogus (33,using powerful dehydrants used, When the alkali mercerized products were washed un- such as phosphorus pentoxide, obtained high nitration and stretched, they gave a cellulose hydrate pattern; washed improved patterns. Trillat (33, 34) found amorphous mastretched, a natural cellulose pattern was obtained. Schra- terial masking the crystalline, but the latter more prominent mek and Schubert (29) found a quantitative relation between the higher the nitration. the x-ray spectrograph and the degree of mercerization. ACKNOWLEDGMENT Their work suggests mercerized cellulose to be a mixture. Khouvine, Campetier, and Sutra (23) showed that their bacThe three commercial pulps used in this investigation teria-produced cellulose membranes were mercerized by 20 were kindly furnished by Harold R. Murdock, director of the per cent carbonate solutions. Nitrated, they gave the usual Research Department of the Champion Fiber Company, patterns for nitrocellulose. Canton, K. C. A satisfactory explanation of mercerization may not be LITERATURE CITED possible as yet; but it is significant that, whatever the origin, the authors obtained practically the same pattern in position (1) B a r n e t t , J. SOC.Chem. I n d . , 40, 8-10T (1921). (2) Clark, IND. ENQ.CHEW,22,474 (1930). and intensity of lines. (3) Davey, Chem. Rev., 6 , 155 (1929). With the acetates of cellulose prepared above 65’ C., (4) Herzog, Ber., 60B,600 (1927). well-defined lines were obtained in all cases. According to (5) Herzog, J . P h y s . Chem., 30,457 (1926). Trillat (32) these are due to a crystalline portion probably the (6) Herzog, KoEZoid-Z., 39, 98 (1926). (7) Herzog, Natunuissenschaften, 12,955 (1924). triacetate. NBray-Szab6 and Susich (26) found that only (8) Hereog, Papier-Fabr., 21, 388 (1923). triacetates and trinitrates show well-defined lines. With the (9) Hersog, Tech.-Wiss. Teil, Papier-Fabr., 23, 121 (1925). acetates prepared below 65’ C., none of the lines was very well (10) Hersog and Jsncke, Ber., 53B,2162 (1920). defined. The line 6.50 A. could not be measured satisfactorily (11) Hereog and Jancke, Z. Physik, 3, 196 (1920). in some patterns. Trillat (55) thinks that generally the ace- (12) Herzog and Londberg, Be?., 57B,329 (1924).
December, 1933
I N D UST R I A L AN D E N G I N E E R I N G C H E MISTR Y
Herzog and NAray-Seabo, 2. p h y s i k . Chem., 130,616 (1927). Hess, Tech.-Wiss. Teil, Papier-Fabr., 22, 401 (1924). Hess, Wochbl. Papierfabr., 55, 2199 (1924). Hess, Zellsfof u.I'apier, 4, 177 (1924). Hess and Trogus, Ber., 61B, 1982 (1928). Hess and Trogus, 2. physik. Chem., B11,381 (1931). Irvine and Hirst, J. Chem. Soc., 121, 1587 (1922). Kats, 2. Elektrochem., 32, 269 (1926). Kats and Mark, Ibid., 31, 105 (1925). Katz and Vieweg, Ibid., 31, I57 (1925). Khouvine, Campetier, and Sutra, Compt. rend., 194, 208 (1932). Levinstein, J . SOC.Chem. Znd., 49,55T (1930). Meyer and Mark, Ber., 61B,593 (1928). Ngray-Ssabo and Susich, 2. p h y s i k . Chem., 134,264 (1928).
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(27) Ritter, IND.ENG.C H E x . , Anal. Ed.. 1, 52 (1929). (28) Sakurada and Hutino, Sci. Papers Inst. P h y s . Chem. Research (Tokyo), 17, N o . 344, 294 (1932). (29) Schramek and Schubert, 2. physik. Chem., B13, 462 (1931). (30) Snell, IND.EXQ.CHEX.,17, 197 (1925). (31) Sponsler and Dore, J . Am. Chem. Soc., 50, 1940 (1928). (32) Trillat, Compt. rend., 186,859 (1928). (33) Trillat, Ibid., 194, 1922 (1932). (34) Trillat, J. phys. r a d i u m , [71 2,65 (1931). (35) Trillat, Rev. gbn colloides, 6, 57, 89, 177 (1928). (36) Trogus, Ber., 64B,405 (1931). (37) Vieweg. Zbid., 57B,1917 (1924). R ~ C E I Y EApril D 18, 1933.
Vapor Pressure and Vaporization of Petroleum Fractions DONALD L. KATZAND GEO. GRANGER BROWN,University of Michigan, Ann Arbor, Mich.
T
HE vapor pressure of a
liquid a t a specified temperature is the pressure under which the liquid is in equilibrium with a vapor. I n the case of a pure substance or single component, the liquid and the vapor p h a s e s are each of the same p o s i t i o n and posed entirely of the pure substance. I n any case the vapor pressure must be determined of an
A 11 major operations of petroleum re$ning in-
corporate llaporization and condensation. this paper methods f o r computing the vapor pressure and vaporization characteristics of petroleum fractions have been critically reviewed, combined, and extended in order to present a useful compilation of the data and now available to the engineer. The use of the modern derelopmenls in thermodynamics, including the application of fugacities, is explained by example and checked against experimental results.
I n the case-of a pure substance or single component it is necessary to fix only the temperature in order to determine the vapor pressure, as the one-component system in two phases has one degree of freedom. I n the case of a multiple-component system it is necessary to fix not only the temperature but also the composition in order to have an invariant system. Therefore, it is imperative that no vaporization of a complex liquid be tolerated in determining the vapor pressure of the liquid, as any formation of vapor would change the composition of the liquid whose vapor pressure is being determined. If this precaution is not taken, the vapor pressure determined is not that of the original liquid but rather of the liquid residue remaining after partial vaporization. EQUILIBRIUM VAPORIZATION When a mixture of hydrocarbons such as a petroleum fraction is heated to a specified temperature and pressure so that part of the material is vaporized and part is liquid, the process is known as equilibrium vaporization if the resulting vapor and liquid are in equilibrium with each other. I n some cases, as when vapor is formed from the surface of oil in storage, the vapor may not be in equilibrium with the entire body of the liquid owing to inadequate agitation, but in practically all steps in the processing of petroleum there is sufficient agitation to insure approximate equilibrium between vapor and liquid phases. For this reason, as well as the fact that equilibrium conditions are the only conditions t h a t may be duplicated or computed, all calculations presented deal exclusively with equilibrium conditions.
Petroleum fractions are composed essentially of hydrocarbans, a n d an of the vapor p r e s s u r e a n d v a p o r i z a t i o n characteristics of the hydrocarbons is the necessary basis for a s t u d y Of the vapor and of vaporization c h a r apressure c ter fractions. V a p o r p r e s s u r e data of the paraffin hydrocarbons are fairly
the data- are scattered and incomplete. I n practice it is important to estimate the vapor pressure of these other types of hydrocarbons and the vapor pressure of all types of hydrocarbons a t higher temperatures. For these reasons it is necessary to extrapolate and interpolate the available vapor pressure data. Many different methods have been proposed for making these interpolations, all of which are based on the vapor pressure data of the normal paraffin hydrocarbons. VAPORPRESSURE DATA The vapor pressure data are extensive and scattered. Complete data and bibliography up to 1928 on the paraffin hydrocarbons are given by Young (86) and by Brown and Coats (11). Robinson (67)is also a useful source of data and bibliography in addition to the International Critical Tables and other tables of reference. Toluene data are given by Young (88) and recently by Krase and Goodman (40). Linder (46)gives data on a number of hydrocarbons over a limited temperature range in the neighborhood of 0" C. Hexane and heptane data over a limited temperature range are reported by Smyth and Engel (70),which are in close agreement with the earlier and more extensive data of Young (87). VAPORPRESSURE RELATIONSHIPS As early as 1855 Kopp (39) stated that the boiling point a t the atmospheric pressure of the adjacent members of a homologous series of liquids differed by a constant amount. This relationship was extended to pressures other than atmospheric by Winkelman (83).
