The Determination of Organic Matter in Air. 



247 



definite intervals the carbonic acid and organic matter present in the 

 air of the room were determined, the analyses being made in the 

 room itself so as to avoid opening the door. The room being un- 

 provided with outside light, one gas jet was kept burning- during the 

 whole of the experiments, but the effect of this on the organic matter 

 may be neglected, for, as previously shown, the combustion of coal 

 gas does not appreciably increase the amount of organic matter. The 

 results obtained are shown below : — 







Outside 



After 20 



After 30 



After 60 



After 100 







air. 



minutes. 



minutes. 



minutes. 



minutes. 



1st experiment 



r co, 



I O.M. 



3-8 

 9-5 



11 -4 



12 9 



14-8 

 14-8 







2nd experiment 



fC0 9 

 [O.M. 







13-1 

 14 2 



23-5 

 15 -9 



28 -2 

 17-0 



3rd experiment 



rco 2 



[O.M. 







17-2 

 13 5 



24-1 

 15-7 



32 1 

 20 3 



Here it is seen that the amount of organic matter becomes greater 

 as the period of vitiation increases, but very much less slowly, so that 

 the increase in the quantity of organic matter is by no means pro- 

 portional to the time. It also increases less rapidly than the carbonic 

 acid. 



(8.) An atmosphere which has been entirely at rest for some time is 

 found to contain less organic matter than it did previously. This is 

 not necessarily entirely due to the settling down of the solid organic 

 dust, but is probably due in part to oxidation. 



The statement made in 'Nature' (vol. 33, 1886, p. 130), in an 

 article on ventilation, to the effect that the organic matter in respired 

 air increases pari passu with, and is therefore estimated by the amount 

 of carbonic acid present, may be true when the average of a large 

 number of determinations is taken, but is certainly very far from 

 being true in individual cases. At any rate the amount of carbonic 

 acid is no certain index of the quantity of organic matter present in 

 an atmosphere (see above). That air in which respiration has gone 

 on for some time gives invariably a higher result than outside air at 

 or about the same time is all that can be confidently affirmed. 



It should not be forgotten that the organic matter in air is most 

 probably partly solid and partly gaseous. The solid obeying a 

 different law than diffusion slowly settles down, whilst the gaseous 

 part, unlike carbonic acid, is most likely an unstable compound or 

 compounds, and readily undergoes oxidation. Experiments were 

 made in regard to this, but they did not give decisive results. 



vol. xli. s 



