﻿METHODS FOR THE DETERMINATIOK OF ORaANIC 



MATTER IN AIR. 



By Dayid Hendricks Bergey, B.S., M.D. 



A nnmber of methods have been devised for the estimation of 

 organic matter in air. The results that have been obtained by these 

 different methods are, however, quite variable even under the same 

 atmospheric conditions. The dijfficulties that were encountered in 

 estimating the quantity of organic matter in expired air, while con- 

 ducting the research on The Composition of Expired Air and its 

 effects upon Animal Life,' demonstrated the fact that some of the 

 methods in use were unsatisfactory. At the suggestion of Dr. Bil- 

 lings some of these methods have been tested and compared as to 

 their reliability and adaptability for hygienic investigations. 



The methods that are now in use fall into two gro^ips. In the first 

 group of methods the organic matter is converted into ammonia either 

 by the Wanklyn, Chapman, and Smith ^ process and estimated with 

 Nessler's reagent ; or by direct nesslerization of the absorbent used to 

 abstract the organic matter from the air ; or, as in one of the methods, 

 the distillate is carried into dilute sulphuric acid and the amount of 

 free acid estimated by titration with deci-normal ammonia. 



In the second group of methods the organic matter is oxidized by 

 boiling with a dilute solution of permanganate of potash, and titrating 

 with oxalic acid solution, as in the estimation of organic matter in water. 



All these different methods are colorimetric in their nature. They 

 are also only indirect methods inasmuch as they afford no clue as to 

 the nature or quantity of organic matter — as such — that is present in 

 the air ; the end-products in all of the methods being of an entirely 

 different nature from the organic matter itself. 



The modifications of the methods of both groups by different experi- 

 menters consist principally in variations as to the form of absorbent 

 used and the modes of absorption, or in the manner of applying the 

 reducing agents. In most instances the modifications of the apparatus 

 employed are of minor importance. 



The methods of the first group have much in common. Chapman ^ 



