THE PURIFICATION OF ACETAMIDE E. C. WACNEK,UNIVERSITY OP PENNSYLVANIA. PHIIADELPHIA, PENNSYLVANIA Complete purification of acetamide by distillation under ordinary pressure is probably impossible, as the temperature required leads to formation of small amounts of acetonitrile and water,' often to discoloration from corks, and as the objectionable odor persists. For purification by crystallization there have been recommended solvents such as ether, chloroform, benzene, and a mixture of benzene and ethyl acetate. The use of ether yields a well-crystallized product, and reduces or removes the odor, but the slight solubility of acetamide in boiling ether makes this method suitable only for small quantities. The other liquids named have in common the disadvantage that their solvent action upon acetamide is excessive, so that upon crystallization the solution "sets." The crystals cannot be properly separated from the mother-liquor by suction, due to its small volume and high concentration and to the hygroscopic nature of the acetamide, nor by washing with the chilled pure solvent, due to the heavy loss this would entail. Somewhat better results have been obtained, following the use of chloroform as solvent, by washing the crystals with ether. The product obtained in any case is likely to be somewhat odorous, wet in appearance, and i t generally melts too low. The method of purification described herewith is based upon the high solubility of acetamide in methyl (or ethyl) alcohol, its sparing solubility in ether, and the fact that a concentrated solution in alcohol, when largely diluted with ether, deposits cr(jsta1s of acetamide in a state of purity. With small quantities of acetamide most of the required ether can he added without separation of crystals, and upon seeding the highly supersaturated solution crystallization proceeds rapidly. When this operation is conducted carefully large crystals may be obtained, the crystallization affording a striking demonstration of supersaturation. With larger amounts of acetamide crystallization usually begins before all the ether has been added. The filtration and further treatment of the recrystallized acetamide are made easy by the nature of the product and the large volume of the mother-liquor. Procedure In a flask dissolve the acetamide in hot methyl alcohol, using 0.5 cc. for each gram of acetamide. If not dear, filter the hot solution rapidly through paper with suction, or through cotton, receiving it in a vessel large enough to permit ten-fold dilution. Wash the flask and filter with warm alcohol, using enough to bring the total alcohol to 0.8 cc. per gram of acetamide. Treat the solution, in the manner described below. with ether in the proportion of 8 cc. to 10 cc. of ether for each gram of acetamide. Introduce the ether at iirst rather slowly and with stirring, but avoid splashing. Hitch and Gilbert, J. Am. Chem. Soc., 35, 1780 (1913). 1135
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With small amounts of acetamide (e. g., 10 to20 grams), and in the ahsence of conditions which will disturb the state of supersaturation, about three-fourths of the ether may be added without separation of crystals or appearance of turbidity. If too much ether is added a t this stage the liquid may become turbid and stratify into two layers, a condition which may be remedied, though, with decrease in the amount of acetamide recovered, by dropwise addition of alcohol until the liquid is again homogeneous. Into the dear supersaturated solution drop a minute crystal of acetamide. If large crystals are desired, allow the covered liquid to remain perfectly quiet and at room temperature after seeding. To obtain small crystals and a higher recovery, stir the liquid after seeding, and chill in an ice hath., In either case. after the initial crystallization has occurred, add the remaining ether and allow to stand about an hour. With hrgcr amounts of acelumide crystallization usually begins after about onefourth or somewhat more of the ether has heen added; otherwise it should be started by seeding. As soon as crystals appear stop the stirring, and allow the liquid to rest until the initial crystallization is about complete. Add the remaining ether rapidly, with vigorous stirring, and chill the liquid thoroughly in an ice hath. Filter off the crystals rapidly with suction, and wash once with dilled ether. Continue the suction only long enough to remove most of the ether, transfer the acetamide to a desiccator, and dry in vacuo or over sulfuric acid. The mother-liquor and wash-ether, if combined and kept for some time in an ice hath, will often yield a second crop of crystals, increasing the recovery several per cent, or mare if the main crystallization occurred a t room temperature.
The product obtained as just described consists of crisp, well-formed needle-crystals, which are dry and without odor. The recovery varies with the quality of the starting material. With very impure acetamide, slushy in consistency, the yield was about 65 per cent. With crude acetamide melting at about 76' the r&overy was 70 to 75 per cent. Recrystallization of pure acetamide permitted recovery of about 85 per cent. Crystallization a t room temperature, or with a larger proportion of alcohol, decreases the yield. Acetamide recrystallized by the above method melted almost invariably a t 82' or slightly higher. In no case did repetition of the crystallization of such material, using pure methyl alcohol' and anhydrous ether, effect any substantial change in melting point. As a melting point of 83' was recorded several times, it seems quite possible that the true value is higher than 82' as usually stated, and certainly it is higher than 81' as given in "International Critical Tables." The range 82-83' given by Hofmann2 probably includes the correct value. The boiling point of material which melted a t 82-83' was 221.5". The values stated were obtained with thermometers certified by the Bureau of Standards, and are fully corrected. There were used the procedures recommended by Mullikea3 The purification of acetamide by the method described appeared to Hofmam, Ber.. 14, 2719 (1891). "A Method for the Identification of Pure organic Compounds." Vul. I, 1904 (Wiley and Sons). Melting point, p. 218; boiling point, p. 221. a
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be about equally successful whether there were used commercial wood alcohol and U. S . P. ether or acetone-free methyl alcohol and anhydrous ether. Ethyl alcohol was used in one trial, and without noticeable change in results. Handsome crystals, whose length was apparently limited by the size of the container, were obtained by use of acetamide, methyl alcohol, and ether in the proportion of 1: 1: 13, i. e., more alcohol than specified above. Somewhat larger yields were obtained when the proportion of the three substances was 1:0.5:10. The quantities of acetamide taken for the experimental trials ranged from 10 to 500 grams. The method described has been uniformly successful in the hands of students during several years, and its use has been responsible for a marked improvement in the quality of acetamide prepared. It appears to be much the easiest and most satisfactory procedure available for the purification of acetamide.
FOR THE NEW YEAR. A DECALOGUE OF AIMS 1. To be independent and non-partisan. 2. To stress the importance of background and perspective in the discussion of public problems. 3. To help cultivate habits of thought and action which will make well-earned leisure enjoyable and not a burden. 4. To illustrate the evils that arise through rkliance upon the theory of "manifest destiny." q 5. To resist the belief t h a t machinery, whether physical machinery or the machinery of organization, is our salvation. 6. To point out the possibilities and the Limitations of the scientific method in the regulation of society. 7 . To insist that good taste is the essence of ~ o v djudment. 8. To contend that cconomic world leadership is a mrans, not an end. 9. To suggest standards t o which aspiring youth can rally. 10. T o be a t once aitical and constructive. -An address by Harold de Wolf Fuller, editor of New York, delivered a t a dinner given him by his friends, quoted fromEducation
Chromite in Canada. The discovery of chromite on the Wigwam River, in the Obonga Lake district of Northern Ontario, is attracting attention. It was found in a peridotyte dyke, extending several thousand feet. The chromium content varies hetween 7 and 27%. A series of massive chromite veins has been found a t some distance from the contact. Four of these veins have widths of 10 in. t o 2 ft., and have been uncovered over a considerable length. These veins average 34% content. Further development will be required t o determine whether these deposits are of commercial value. The only chrome iron ore mined in Canada was located in the Eastern Townships, south of the City of Quebec, hut these mines have not heen operated for some & ind. years.-Chem.
