﻿OEGANIC MATTER IN AIR. 7 



perature than the surrounding air, about 43° C, as this was found to 

 facilitate the oxidation of the organic matter. The best results were 

 obtained with acid permanganate solution. The accuracy of the 

 method diminishes with the concentration of the permanganate 

 solutions — a solution containing 0.026 mg.K M n "^ to the litre being 

 most satisfactory. 



Some of the methods which have been here reviewed have been 

 tested in this laboratory a number of times in order to determine their 

 reliability. In most instances the same method of absorption was 

 resorted to for the estimation of either the ammonia or the reducing 

 power of the organic matter in the air. It was possible therefore 

 to estimate the quantity of organic matter in the air in terms of both 

 the end-products which have served thus far for the estimation of 

 organic matter by the various experimenters. 



In those methods in which the organic matter is converted into free 

 and albuminoid ammonia the retort and condenser used for the distil^ 

 lation process are previously rendered free from ammonia by the pro* 

 longed distillation of distilled water that contains but very small 

 proportions of ammonia. The absorbent material, whatever the form 

 that has been used, is transferred to the clean retort and diluted with a 

 sufficient quantity of twice distilled water to bring the whole amount 

 up to 500 c. c. The preparation of sufficient quantities of twice distilled 

 water having a low ammonia-content is not always an easy matter.. 

 This is especially the case with the laboratory water-supply. The 

 sewage contamination of the water supply is so marked as to make it. 

 impossible to remove all the ammonia in the second distillation, owing- 

 to the presence of considerable quantities of urea in it. By using- 

 spring water this difficulty was largely obviated. In each determina- 

 tion it is necessary to deduct the ammonia- content of the distilled water 

 that was used to dilute the absorbent material from the results obtained 

 for the determination. 



In those methods in which the reducing power of the organic matter 

 upon permanganate was determined the process was carried out in a 

 porcelain casserole which had previously been cleansed by boiling with 

 some of the permanganate solution. The strength of the solution of 

 permanganate of potash employed was 0.4 g. to the litre of water, and 

 was titrated before each experiment against a solution of oxalic acid 

 containing 0.7875 g. to the litre of water, and 10 c. c. of which 

 equalled 1 mg. of oxygen. In these methods it is also necessary 

 to make deductions from the results obtained for each determination 

 for the amount of oxygen consumed by the organic matter in the twice 

 distilled water that had been used to dilute the absorbent material to 

 100 c. c. In each determination 6 to 8 c. c. of permanganate solu- 



