1859.] on the Estimation of the Organic Matter of the Air. 91 



drops which are poured in will probably be decolorised at once ; a few 

 drops more must then be added ; if they become decolorised a few more 

 must be used ; and so on until there is a perceptible amount of colour 

 remaining. When this occurs, the experiment is concluded. The 

 amount of the reagent used is then read off from the graduated mea- 

 sure. If the liquid be of the proper strength, and the bottle the re- 

 quired size, the number of grains gives tlie comparative quantity at 

 once. Sometimes the amount of organic matter is so small that there is 

 no appreciable action, on even the smallest amount of solution by one 

 vessel of air. In this case it is necessary to fill the bottle several times. 

 The mode of doing this is apparently extremely rude, but the results 

 are such as not to demand a finer method at present. A finer method, 

 of course would need little ingenuity to contrive. At present I merely 

 remove the stopper and fill again with air as before. During the period 

 of filling the vessel the surface of the liquid is reduced to its smallest 

 amount, and the change it undergoes is either inappreciable, or so 

 constant as not to affect the results. 



In analysing the air in this manner, it is found that a decided result 

 is attained in about five minutes. Sometimes the result is decided in 

 one : that is, there is a termination to the rapid action. This 

 peculiarity is probably to be explained by the following experiments. 

 If we pour decomposing matter on the permanganate solution, it is 

 rapidly destroyed. If the matter be not in a state of decomposition the 

 action is much slower. 



These different results promise a mode of dividing the organic 

 matter of the air into classes according to its quality. These facts are 

 mentioned merely as germs of a future inquiry. In large towns where 

 coals, containing much sulphur, are burnt, the sulphurous acid takes 

 the oxygen of the chameleon, and an apparently large amount of 

 organic matter results. This sulphurous acid is of itself an impurity, 

 perhaps as hurtful as some kinds of organic matter. 



We measure by this means the amount of oxygen needful for the 

 oxidisable matter of the atmosphere, and all such matter is impurity, 

 in some places entirely organic, in others, such as towns, mixed with 

 inorganic gases. 



Some of the principal results obtained by this method were as 

 follows : 



RELATIVE QUANTITIES OF ORGANIC AND OTHER OXIDISABLE MATTER 

 IN THE AIR OP* 



Manchester (average of 131 experiments) .... 52 9 



„ All Saints, E. wind (37 experiments) . . 52*4 



„ „ W. wind, less smoky (33 expts.) . 49*1 



* A few of these results were published in the "Athenaeum" during last 

 summer. The present numbers are somewhat higher, being reduced, for the sake 

 of uniformity, to correspond to a vessel of 100 cubic inches. 



