Determination of Carbon in Organic Compounds Modification of the Combustion Vessel A. K. PARPART AND A. J. DZIEMIAN Princeton University, Princeton, N. J.
T
HE carbon content of a variety of nonvolatile organic
Figure 1. I n addition, the arm of the combustion vessel is held rigidly in place by means of a rubber stopper, E, through which it passes, and which fits snugly into the top of D and is kept in osition by means of an aluminum plate, F. Screws fasten F to a Eakelite plate, G, attached to the cup of the extraction chamber. Thus the combustion vessel may be easily and rigidly attached to the extraction chamber.
compounds can readily be determined b y the manometric technique of Van Slyke and Neil1 (2). The method described involves the use of a combustion vessel, A (Figure I), adapted from the design of Backlin (1) by Van Slyke, Page, and Kirk (S).
A
F
FIGURE1. MODIFIED COMBUSTION V~SSELFOR CARBONDETERMINATION Details of Bakelite attachment,-G, to cup are shown in insert, top view
Carbon dioxide-freelsodium hydroxide (0.5 M ) is admitted into the extraction chamber, C, by means of a soda-lime protected separatory funnel at the cup, D. Upon removal of the separatory funnel the combustion vessel, A, is fitted to the cup as described below. The carbon dioxide liberated by combustion is absorbed by the sodium hydroxide, after which gases other than carbon dioxide are removed under mercury through the side arm, B. The combustion vessel is replaced by a buret and a measured uantity of lactic acid is admitted to the extraction chamber. garbon dioxide is freed and the pressure a t a known volume measured. The carbon dioxide is reabsorbed by strong sodium hydroxide and the pressure measured a t the same volume. The pressure of carbon dioxide is secured by the difference between the two readings. A detailed description is given by Van Slyke, Page, and Kirk (3). Van Slyke et al. (5)attach the combustion vessel to B by rubber tubing. With this technique accurate analyses may be obtained, but leaks occur around the rubber tubing with sufficient frequency to invalidate many of the results, and the authors have found it more satisfactory to attach the combustion vessel to the extraction chamber through D. This necessitated a slight change in the design of the arm of the combustion vessel as pictured in
A rubber tip, HI covered by a layer of mercury, prevents as leaks around the tip of the arm of the combustion vessel. 8 y screwing down the aluminum plate this rubber tip is seated securely in place. As a further precaution the stopper, I , of the combustion vessel is sealed with mercury, K. T h e principal advantage of this new design lies in the fact that i t removes all possibility of leaks a t the point of union between the combustion vessel and the extraction chamber. The method of analysis is identical with that of Van Slyke, Page, and Kirk (3) except that the unabsorbed gas in the extraction chamber is ejected through B under mercury instead of through D.
Literature Cited (1) BacMin, E., Biochem. Z.,217,483 (1930). (2) Van Slyke, D. D., and Neill, J. M., J. Biol. Chem., 61, 523 (1924). (3) Van Slyke, D. D., Page, I. El., and Kirk, E., Ibid.,102, 635 (1933).
R ~ C E I V ESugust D 29, 1938.
107
