ANALYTICAL E D I T I O N
322
employed p-toluene sulfonic acid for breaking u p the acetylated compound. The method described in this paper is a modification of the Perkin method. It has none of the disadvantages of the original method, and is an improvement over the modified procedure employed b y Freudenberg and Harder. Using the technic described i t has been possible to obtain quantitative results not only with -0-acetyl but also with -N-acetyl compounds.
APPARATU~ The apparatus used is illustrated in Figure 1. I t is constructed of Pyrex glass and consists of a reaction flask D, which is provided with an inlet tube, B, and stopcock, d‘. D is placed in water bath M , which is heated with microburner Q. Connection between D and condenser F is made through interchangeable ground-glass joint E (No. 11) and is held fast by means of springs 0. Condenser F is connected through glass tube H to condenser G. K is a 300-cc. Erlenmeyer flask upon which two marks have been placed indicating a volume of 100 ahd 150 cc., respectively. During the distillation L serves as an ice bath, and during the hydrolysis of the ethyl acetate, as a water bath. J is a rubber stopper, the opening of which has been lubricated with glycerol so that it can readily slide up and down tube I . N is a two-wa stopcock through which cold water for condenser F is p a s s e l By turning N and opening pinchcock P it is possible to drain the water immediately from F. A is a 500-cc. Erlenmeyer flask, partly filled with aldehyde-free 95 per cent ethanol and used or generating alcohol va or. It is heated by means of an electric hot plate, not shown on tEe drawing.
Vol. 6 , No. 5
Instead of refluxing the solution in D for 15 minutes, it is refluxed for 2 hours. The water in condenser F is then drained, and alcohol vapor from generator A is allowed to pass through the solution contained in reaction flask D. This operation is continued until the volume of the solution in K measures 100 cc. During this distillation the heating of M is so regulated that the volume of the reaction mixture in D is reduced one-half. C is then shut off, and cold water is again circulated through F. The solution in D is then refluxed for 30 minutes, after which the cold water circulating through F is shut off, the jacket of the condenser F is drained, and a current of alcohol vapor from A again passed through the solution in D. This operation is continued until the volume of the li uid in K measures 150 cc. The refluxing of the solution in K a n j the determination of the excess of potassium hydroxide sdution are carried out exactly as described above for -0-acetyl compounds. The results obtained with several -0-acetyl compounds
and with acetanilide are given in Table I. TABLE I. DETERMINATION OF ACETYL WEIQHT OF
COMPOUND
SAMPLE
Acetyl dehydrotoxicarol Cellobiose octaacetate Acetanilide Acetanilide
PROCEDURE FOR -O-ACETYL COMPOUNDS The weighed sample (0.3 to 0.4 gram) is laced in reaction flask D to which are also added 5 rams of togenesulfonic acid,’ a small piece of unglazed tile, a n t 2 5 cc. o f & per cent aldehydefree ethanol (prepared by the method of Stout and6Schuette, 4). Into receiver K , 25 cc. (accurately measured with a pipet) of an alcoholic potassium hydroxide solution (approximately 0.2 N ) and a small piece of unglazed porcelain are put. J is moved up close to the inner seal of G, leaving K open to the atmosphere. K is surrounded with crushed ice contained in L,which is supported by means of a ring and stand. The height of the ring is so adjusted that I reaches close to the bottom of K. E is lubricated with stopcock grease and is attached to F with springs, 0. Cold water is circulated through both condensers, and D is placed in water bath M , and the reaction mixture is refluxed for 15 minutes. The water in condenser F is then drained, stopcock C is opened, and a slow stream of alcohol vapor is allowed to pass into D from generator A . This operation is continued until the total volume in K measures 150 cc. During the distillation, M is heated with microburner Q at such a rate that a t the end of the distillation the volume in D is reduced ap roximately one-half. K is then lowered so that the end of P i s above the level of the liquid. Stopcock C is shut off, and the rubber tube attached to generator A is disconnected from B. D is detached from F , and J is lowered until it is approximately 2 inches (5 cm.) from the lower end of I and is securely attached to K. The ice in L is re laced with hot water, and the distillate is refluxed for one-half tour. During this period L is heated with a microburner. K is then disconnected, diluted with distilled water, and the unused potassium hydroxide determined by titration with 0.1 N acid, phenolphthalein being used as the indicator. A somewhat sharper end point is obtained by running in a known excess of 0.1 N acid and ,determining this excess by titration with 0.1 N alkali. A blank determination is made following the procedure above described, except that no sample is added to D. From the blank determination the normality of the alcoholic potassium hydroxide solution is accurately determined. The number of cubic centimeters of 0.2 N potassium hydroxide solution used when multiplied by 0.86 and divided by the weight of the sample gives the percentage acetyl in the compound.
PROCEDURE FOR -N-ACETYL COMPOUNDS The analytical procedure described above is modified as follows: 1 Thia is purified as follows: A strong aqueous solution of p-toluenesulfonic acid is placed in a distilling flask which is attached to a condenser, and a current of steam passed through the solution until the distillate coming over no longer reacts acid. The residual solution of the sulfonic acid is concentrated on the steam bath and allowed to crystalliee. The crystals are filtered off and dried in a vacuum desiccator over sulfuric acid.
0.2 N XOH
U
~
ACETYL D Found Calculated
Cram
cc.
%
%
0.4000 0.4000 0.2000 0.3000 0.3500 0.2000 0.3500 0.3500
10.87 10.88 5.35 6.95 3.90 23.9 13.1 13.08
23.3 23.3 23.0 17.05 9.58 51.3 32.1 32.1
23.1 23.1 23.1 17.4 9.66 60.74 31.8 31.8
LITERATURE CITED (1) Freudenberg and Harder, Ann., 433,230 (1923). (2) Meyer, H., “Analyse und Konstitutionsermittlung organisoher Verbindung,” 4th ed., pp. 670-83,J. Springer, Berlin, 1922. (3) Perkin, Proc. Chem. SOC.,20, 171 (1904);J. Chem. Soc., 87, 107 (1905). (4) Stout and Sohuette, IND.ENQ.CHEM.,Anal, Ed., 5, 100 (1933). ( 5 ) Sudborough and Thomas, Proc. Chem. Soc., 21,88 (1905). (6) Wensel, ref. 2,pp. 678-81. REOEIYEDMay 8, 1934. 238th Contribution from the Color and3Farm Waste Division, Bureau of ,Chemistry and Soils, U. S. Department of Agriculture, Washington, D. C.
Suction Device LOUISCOHEN College of the City of New York, New York, N. Y.
I
N laboratory filtrations employing suction, i t is fre-
quently desired to introduce the filtrate directly into the Erlenmeyer or any other flask. For such a purpose, the piece of apparatus shown in the illustration as used with a Walter crucible holder has proved convenient. This device is particularly applicable in the analysis of reducing sugars.’ T h e a p p a r a t u s may b e r e a d i l y constructed from a Pyrex test tube, b y attaching a side arm at a convenient distance from its mouth, expanding the mouth to fit a Walter crucible holder, and cutting the test tube at a convenient distance from the bottom, to allow a portion of the holder stem to extend beyond the so-called s u c t i o n funnel stem. RECEIVBD June 9, 1934. 1 ASEOC. O5cial Agr. Chem., Official and Tentative Methods, pp. 379-80 (1930).
