Reprinted from the American Journal of Physiology 

 Vol. XXXII June 2, 1913 No. II 



A NEW METHOD AND APPARATUS FOR THE 



ESTIMATION OF EXCEEDINGLY MINUTE 



QUANTITIES OF CARBON DIOXIDE 1 



BY SHIRO TASHIRO 



[From the Department of Biochemistry and Pharmacology, the University of Chicago, and the 

 Marine Biological Laboratory, Woods Hole, Mass.] 



IN connection with the study of the metabolism of the nerve fibre, 

 I undertook, at the suggestion of Prof. A. P. Mathews, to work 

 out a method for the detection of exceedingly minute quantities of 

 carbon dioxide. Following a suggestion made by Dr. H. N. McCoy, 

 a very simple method was devised, which I reported first to the 

 Chicago Section of the American Chemical Society; 2 later in con- 

 junction with Dr. McCoy, its further details were reported to the 

 Analytic Section, 3 of the Eighth International Congress of Applied 

 Chemistry. The principle of the new method is as follows : 



1. Exceedingly minute quantities of carbon dioxide can be precipi- 

 tated as barium carbonate on the surface of a small drop of barium 

 hydroxide solution. 



2. When a drop of barium hydroxide is exposed to any sample of 

 gas free from carbon dioxide, it remains perfectly clear, but when 

 more than a quite definite minimum amount of carbon dioxide is intro- 

 duced, a precipitate of carbonate appears, detectable with a lens. 



3. By determining, therefore, the minimum volume of any given 

 sample of a gas necessary to give the first visible formation of the 

 precipitate, its carbon dioxide content can be estimated accurately, 

 since this volume must contain just the known detectable amount of 

 carbon dioxide. 



1 One of these apparati was described at the biochemical section, Eighth 

 International Congress of applied chemistry, September, 1912; see also, Journal 

 of biochemistry, 1913, xiv, p. xli. 



2 May 18, 1912. 



8 Original Communication: Eighth International Congress of applied chemis- 

 try, 1912, i, p. 361. 



