NOVEMBER 15, 1937
ANALYTICAL EDITION
tube. If oxygen is retained in the residual carbon it does not appear to yield to these increasingly strenuous heat treatments. The carbonaceous residue is undoubtedly active, so that it did not seem feasible to remove it from the hydrogenation tube in order to make a carbon analysis, since it would probably rapidly adsorb both oxygen and moisture from the atmosphere. I n the analysis of a substance such as sucrose, which has a high oxygen content and which readily loses water on heating, it was thought that perhaps carbon monoxide or dioxide was lost by the reversal of the following equilibria caused by the sudden appearance of considerable amounts of water: CO CO,
3Hz .S CHI + HzO ++ 4H2 CHd + 2H20 $
It was experimentally proved that this was not the case, a t least for the carbon dioxide reaction. I n several analyses an Ascarite-soda lime tube, placed after the Drierite tube, showed no increase in weight over that of a blank determination, so that no carbon dioxide escaped. To get experimental evidence concerning the reversal of the carbon monoxide reaction it would be necessary to determine very small amounts of carbon monoxide in the presence of large quantities of hydrogen, which is difficult. It also did not appear likely that carbon monoxide would escape reduction, since the literature indicates that carbon monoxide is converted to methane, under conditions similar to those used here, more easily than is carbon dioxide. Hence, if carbon dioxide does not escape reaction i t is not likely that carbon monoxide would escape. An increase in the rate of hydrogen flow to 10 cc. per minute, using a total of 800 cc., also failed to improve the results. The investigation of sucrose, and other substances which behave similarly on pyrolysis in hydrogen, is being continued and will be reported later. After a number of sucrose samples have been analyzed, the deposit of carbon in the hydrogenation tube, which renders visibility difficult, is removed as follows: The glass plug and boat and also the nickel gauze roll are removed. If the nickel gauze contains a deposit of carbon ib is burned off in a strong Bunsen flame. The whole gauze is oxidized by heating in a Bunsen flame and then reduced in a stream of hydrogen by heating t o dull redness in a hard-glass combustion tube. The hydrogen in the quartz hydrogenation tube containing the carbon deposit is then displaced by nitrogen. The nitrogen (water-pumped) is taken from a high-pressure cylinder and assed through a Pregl pressure regulator, a bubble-counter U-tuie, filled like the one in the hydrogen purifying train, and then is passed into the end of the hydrogenation tube, the connection being made with a rubber stop er. During this procedure the hydrogen is completely shut o g a t the three-way stopcock and the catalyst furnace is at room temperature while the cracking furnace is heated. When the hydrogen is all displaced by nitrogen, air is admitted from the gasometer and passed into the hydrogenation tube through the three-way stopcock after emerging from the air purifying train, which is identical to that used for the hydrogen except that no preheater is used. By heating the portion of the tube containing the carbon deposit with a Bunsen burner and wire gauze the carbon is readily removed. The cracking furnace is then allowed to cool, hydrogen is passed to displace the air, the nickel gauze roll is reinserted, and then both furnaces are reheated, the methanation catalyst being heated to 400" C. during the reduction of any nickel oxide which might have formed during the burning-out process. After reduction overnight, or Ion er, the temperature of the catalyst furnace is reduced to 350" and if the blank determination is satisfactory the apparatus is ready for use.
6,
Acknowledgments The author wishes t o express his appreciation t o B. B. Scott for designing the electrical furnaces used in this inveatigation and to J. A. Thompson for their construction.
539
Literature Cited (1) Goodloe, P.,and Frazer, J. C. W., IND. ENQ.CHEM.,Anal. Ed., 9, 223-5 (1937). (2) Hennig. H., Chem. Fabrih, 9. 239-41 (1936). (3) Inaba,-T., and Abe, Y.,'S.' SOC.Chem. ind., Japan, 39, 91B (1936). (4) Eirner, W. R., IND. ENO.CHEM.,Anal. Ed., 6, 358-63 (1934) 7, 363-5 (1935); 7, 366-8 (1935); 8, 57-61 (1936). (5) Zbid., 6, 358-63 (1934); 8, 57-61 (1936). (6) Lacourt, A., Bull. SOC.chim Belg., 43, 73-92 (1934). (7) Lindner, J., and Wirth, W., Ber., 70, 1025-38 (1937). (8) Meulen, H. ter, Rec. trav. chim., 53, 118-25 (1934); Bull. uoc. chim., (5) 2, 1692-4 (1935). (9) Meulen, H. ter, Rec. traw. chim., 53, 118-25 (1934). (IO) Zbid., 41, 509-14 (1922); Bull. SOC.chim.,(5) 2, 1692-4 (1935). (11) Niederl, J. B., and Whitman, B., Mikrochemie, 11, 287, 295-6 (1932); Niederl, J. B., and Roth, R. T., IND.ENO.CREW, And. Ed., 6, 272 (1934). (12) Russell, W. W., and Fulton, J. W., Zbid., 5, 384-6 (1933); Russell, W. W., and Marks, M. E., Ibid., 6, 381-2 (1934); 8, 453-5 (1936); Marks, M. E., Zbid., 7, 102-3 (1935). (13) Unterzaucher, J., and Burger, K., Ber., 70, 1392 (1937).
RECEIVED August 30, 1937. Presented before the Microchemical. Reotinn .. ..-. at the 9lst Meeting of the American Chemical Society, Kansas City, Mo., April 13 to 17, 1936.
The Determination of Acetyl, Especially in 0-Acetyl Compounds E. P. CLARK Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture, Washington, D. C.
IN
A RECENT communication (1) the writer presented a general method for the determination of acetyl, based upon the principle of an alkaline, alcoholic hydrolysis of an acetyl compound, followed by acidscation and distillation of the liberated acetic acid. For the distillation the alkali was neutralized with enough strong magnesium sulfate solution containing sulfuric acid, so that the reaction mixture had a volume of 20 cc. This was steam-distilled a t constant volume until 50 cc. of distillate were obtained. The acetic acid which came over under these conditions represented 95.7 per cent of the total acetic acid formed by the hydrolysis of the acetyl compound. The procedure gives satisfactory results, but if it is carried out as previously outlined, except that the distillation of the liberated acetic acid is conducted a t such a rate that the reaction mixture is concentrated to approximately 15 cc. during the collection of the 50 cc. of distillate, the entire quantity of acetic acid is found in the distillate. This procedure is simpler and more conveniently conducted than if the distillation is carried out a t constant volume; the use of an arbitrary factor is eliminated and the results are as accurate as those obtained by the former method. I n the new procedure a blank must be run upon the reagents for a given set of conditions, as wm recommended in the case of N-acetyl compounds.
Literature Cited (1) Clark, E. P., IND. ENO.CHPM.,Anal. Ed., 8, 487 (1936). RBOIUIYIUD September 22, 1937. Presented before the Microchemical Section a t the 94th Meeting of the American Chemical Society, Roohester, N. Y.,September 6 to 10, 1937.
