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METHODS FOE THE DETERMINATION OF 



organic matter forms but an exceedingly small proportion of the total 

 organic matter. 



2. The attachment of a dust-filter of asbestos to the absorption 

 apparatus produces results that are constantly lower than those ob- 

 tained without the dust-filter. 



"3. The most reliable method for the estimation of organic matter in 

 air is that known as Kemsen's method, and is called Method Ill-a in 

 this research. The pumice-stone seems to be the best form of absor- 

 bent material because it can be thoroughly cleansed by heat without 

 changing its condition or usefulness. 



4. Those methods which determine the organic matter from its redu- 

 cing action on permanganate do not seem to afford as satisfactory 

 results as those in which the organic matter is estimated as ammonia. 



This work was performed while holding the Thomas A. Scott 

 fellowship in Hygiene in the Laboratory of Hygiene, University of 

 Pennsylvania. I desire to express my thanks to Dr. John S. Billings, 

 Director of the Laboratory, and to Dr. A. C. Abbott, First Assistant, 

 for the valuable suggestions and assistance with which they favored 

 me during the progress of the work. 



Fig. 1. — Apparatus used with Methods I, V, and VI. This apparatus consists 

 of : a— a stative which supports the Pettenkofer absoi-ption tube containing the 

 absorbent material ; 6— the gas-meter which measures the volume of air aspirated 

 through the apparatus ; and c— a Chapman water pump, by means of which a 

 slow, steady current of air is maintained through the apparatus. 



