INDUSTRIAL A N D ENGINEERING CHEMISTRY
August, 1924
853
Notes on the Preparation of Standard Cellulose’*’ By A. B. Corey and H. Le B. Gray EASTMAN KODAK Co., ROCHESTER, N. Y.
In Expts. B, E, F , and H the method as recommended by HILE preparing standard cellulose in this laboratory according to the method given in the report of the the committee was strictly adhered to, except that in F 75 Committee of the Division of Cellulose Chemistry of grams of cotton were used instead of 100 grams. the American Chemical Society,s Professor Hibbert suggested A and B show the effect of previous bleaching and appear that we offer a criticism of the method as given, for the pur- to confirm the work of Simonsen. H and K apparently show pose of promoting a discussion which might lead t o an im- the injurious effect of the bleach. provement in the standard obtained. The method used in L gave excellent results, although the I n the procedure as given by the committee it is recom- ash is somewhat high. This may be due to extraction of mended that 100 grams of cotton be put “loosely” in a nickel- silica from the Pyrex glass beaker by the alkali. The experiscreen container and boiled in 3000 cc. of solution. A con- ment will be repeated using apparatus made entirely of nickel. taiher of a size to permit total immersion in 3000 cc. of solu- There is also a possibility that the high ash is due to insuffition, with allowance for the vertical motion, is too small to cient washing. allow 100 grams of cotton to have the freedom of motion SUGGESTED METHOD which the writers believe it ought to have. They therefore recommend that the amount of solution be increased, thus This method is offered tentatively for consideration and making possible the use of a container of such a size as will criticism. allow the cotton to move freely about in it. S i m o n ~ e n working ,~ on easy bleaching Scandinavian sulOne hundred grams of carefully picked Wannamaker’s Clevefite pulp, found that bleached cellulose is very considerably land are extracted in a Soxhlet for 6 hours with 95 per cent ethyl attacked by bleach solutions, especially in the concentrated alcohol, a t such a rate that the alcohol is siphoned every 30 form. This would lead to the view that the bleach solution minutes. It is then extracted with ether for 6 hours, the liquid changing every 30 minutes. causes a pronounced change in the cellulose. It is a wellAfter the extraction the cotton is placed in the nickel-screen known fact that bleach tends to oxidize cellulose. There- basket and treated with 3000 cc. of a 1 per cent sodium hydroxide fore, it would seem advisable to omit bleach if possible. solution which has been previously boiled to remove air. It is TABLEI
W
SAMPLE ( A ) Raw linter purified by manufacturer ( B ) Raw linter repurified by A. C. S. method (C) Raw W. C.’
Moisture
Ash
%
% 0.26 0.19 0.19 0.19 1.26 1.39 0.13 0.13 0.15 0.11
{::E 4.07 (3.92 3.49 3.91
(F) W. C. purified by
A. C. S. method 75 grams (G) Extracted with alcohol, then ether Purified A. C. S. method, soap 2 hours ( H ) W. C. purified by A. C. S. method ( I ) Hospital brand Writer’s analysis from Hibbert Hibbert’s analysis ( J ) W. C. extracted, purified by A. C. S. method, soap 2 hours. Bleach omitted ( K ) One half of ( H ) . Bleach omitted
3
(L) W. C. extracted.
Bleach omitted
1 per cent alkali
( M ) Average analysis of A. C. S. standard a b
in the committee’s report W. C. = Wannamaker’s Cleveland. The alkali solution did not penetrate well
Alpha Cellulose
%
0.17 0.15 0.10 0.11 0.15 0.17 0.11 0.12 0.25 0.26 0.26
99.07 99.11 94.29 93.18 96.25b 96.12b 98.36 98.67 98.84 98.96 98.79 98.88 98.58 98.72 98.78 98.90 98.70 98.83 99.15 99.28 99.79 99.78 100.28 100.08 99.74 99.88 99.84
0.10
99.50
0.10 0.10 0.11 0.10
The writers are of the opinion that it would be better to omit the use of rosin soap, on the ground of possible absorption and the introduction of impurities.
EXPERIMENTAL WORK Linter and Wannamaker’s Cleveland cotton6 was used. The results are given in Table I. 1 Presented before the Division of Cellulose Chemistry a t the 67th Meeting of the American Chemical Society, Washington, D. C., April 21 t o
26, 1924. 2 Communication No. 206 from the Research Laboratory of the Eastman Kodak Company. 8 THIS JOURNAL, 16,748 (1923). 4 Papier-Ztg., 38, 3523 (1913); C . A , , 8, 1202 (1914). 6 Obtained through the Massasoit Manufacturing Co., Fall River, Mass., from the Model Seed Farm, St. Matthews, S. C.
Cellulose No.
Hydrolysis No.
Nitrogen
0.20 0.28 0.39 0.36
3.17 3.49 4.69 5.07
0.78 0.84 0.71 0.64 0.66 0.61 0.78 0.62
0.20 0.25
2.54
0.016 0.016 0.009 0.006 0.17 0.1s 0.004
0.29 0.29 0.24 0.24
3.09 3.09 2.54 3.33
0.01
0.62 0.55 0.34 0.39 0.45 0.32
0.24 0.30
0.21 0.13 0.17
0.27 0.24 0.28
0.29
0.29
2.79
None
Copper
No. 0.31 0.54 2.13 2.29
%
0.05
0,012 0.009
Furfura
% 1.65 1.08 0.77 0.81
0.63
0.72 0.61 0.61 0.57
0.25 0.26
Not sufficient to run
boiled for 6 hours, during which time 3000 cc. of fresh 1 per cent sodium hydroxide solution are run in. This is accomplished b y having a flask containing the solution, which is maintained a t the boiling point, a t such a level that the liquid may be siphoned into the beaker containing the cotton. The fresh solution enters a t the bottom of the beaker while the old solution is removed from the top by a constant-level overflow. The rate of flow is regulated so that i t takes 6 hours for the fresh solution t o flow in. By this method the products extracted by the solution are continually removed. When the solution in the flask is nearly gone, a small portion of distilled water that has been previously boiled is added. This is repeated several times and the flask is then filled with distilled water (previously boiled), andthe cotton washed in this manner. Water is continually added in this way until the cotton is thoroughly washed. Thus during the period of treatment and washing, the cellulose is not exposed t o the air. The cellulose is then drained and removed from the container. It is washed in three changes of distilled
Vol. 16, KO.8
INDUSTRIAL AND ENGINEERING CHEMISTRY
854
water, which is sucked off each time on a Buchner funnel and the cellulose then air-dried.
It will be noticed that Sample L prepared in this manner gives a very high cellulose content, a very low corrected copper number, and an average cellulose number. The ash is too high. During the course of the work it was noticed that the cellulose which had been bleached always imparted to the solution a bright lemon-yellow color when it was treated with 17.5 per cent sodium hydroxide solution in the cellulose
determination, while the unbleached did not. The lemonyellow color appears to be due to the presence of cellulose which has been oxidized.6 While we realize that working with such a compound as cellulose a sufficient number of samples have not been treated and analyzed to offer rigorous proof of our results, we feel that they indicate very strongly that the use of bleach in the preparation of a standard cellulose is very harmful. 8
Worden, “Technology of Cellulose Esters,” 1921, p. 165.
A New Micromelting Point Apparatus’ By J. F. Clevenger BUREAUO F CHEMISTRY, WASHINGTON, D. C.
N T H E work on microsublimation of plant products in the Pharmacognosy Laboratory, crystalline sublimates in a relatively pure state were frequently obtained. The minute quantities of material available and the consequent limitations in applying a chemical test made a method for determining melting points accurately of inestimable value. As a determination of the melting point by the U. 5. P. method2 was often impossible because of the small quantities of sublimates obtained, an apparatus which would permit direct observation of individual crystals by the microscope while the melting point was being determined was devised. A variety of warm stages and incubators now on the market might be used for the a p p r o xi mate determination of low melting points. Other forms of micromelting point apparatus, described by Cram,3 FIG.I-APPARATUS IN POSITION AS USED O N Brant,4 C h a m o t , 6 THE MICROSCOPE STAGE M a v r h o f er . 6 a n d others, make it possible to obtain approximate melting points of microscopic quantities of substances. An apparatus developed by Howard,7 usefur over a wide range of temperature and giving comparatively accurate results, was unsatisfactory because of the difficulty of so confining the heat as to avoid injury to the stage of the microscope. This difficulty was almost entirely overcome by the changes incorporated.
I
the coils are fastened are insulated with asbestos paper. The wire that passes diagonally over the coils is insulated by short, beadlike tubes of asbestos paper held in shape by gluing with sodium silicate. Where necessary, the rest of the unit is insulated by suitable pieces of mica. Between the heaters a heat conductor projecting from one side is inserted in a slot in the object unit when the apparatus is in operation. This arrangement permits ready separation of the units, thereby facilitating rapid cooling of the object unit for subsequent determinations. The heating units permit ready replacement when necessary. The presence of an air chamber in the under part of the object unit reduces heat conduction and consequent injury to the stage of the microscope. Handles constructed of compressed fiber facilitate the removal of the heating unit and the cover of the object chamber. The apparatus is covered with asbestos board glued to the metal surface with a solution of sodium silicate. This reduces radiation and protects the microscope. Cover glasses 12 mm. in diameter reduce radiation from the object chamber and permit observation of the melting point. Melting temperatures up to 400’ C. may be determined. By the use of a rheostat in series with the apparatus7 and a
COVrR, (RCVFRSED)
APPARATUS The apparatus is made of brass of convenient size (10 X x 4 em.) in two separable parts, the heating unit and the object unit. The heating unit, which consists essentially of two electric heaters, is controlled by a three-heat switch. The heaters are made of nichrome wire 0.32 mm. in diameter and approximately 7 meters long, wound in coils approximately 5 mm. in diameter, and passed through openings in a supporting strip of mica. The cross bars of the frame to which 10
Received April 14, 1924. U. S. Pharmacopeia, IX,596 (1916). 8 J . Am. Chem. Soc., 34, 954 (1912). 4 2. Microskopie, 30, 479 (1913). 6 “Elementary Chemical Microscopy,” 1921, p. 218. 6 P~QWZ Presse, . Folge 8 and 10, 1-6 (1922). 7 Viehoever, J . Assoc. Oficial A g r . Chem., 6, 477 (1923).
FIG.
2-APPARATUS
SEPARATED INTO ITS
TWO
UNITS
AND
COVER
three-heat switch the rate of temperature increase may be readily controlled. The melting points of several substances determined by this apparatus and those reported in the literature are given in the following table:
1
2
a b c
MELTINGPOINTS Determined Regorted SUBSTANCG c. C. Coumarin 67 67a Vanillin 80 80 to 81a 109 109 t o 1115 Resorcin Pyrogallol 132 132.6 to 133.5a Santonin 169 t o 170 170a Phenylcinchoninic acid 210 About 21Ob Cedrin 263 t o 265 265c Anthraquinone 286 285 t o 286a Rosenthaler “Die Chemische Analyse,” 1924. U. S. Pharm’aco eia IX 20 (1916). J . Bid. Chem., f4, 3’3 (1616).
