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mode of action of charcoal on putrid emanationSyit will 

 be necssary to obtain some definite notion of the com- 

 position and properties of the organic compounds to 

 which they owe their noxious influence. Experiments 

 made so long ago as 1846 and 1848, when engaged m 

 an inquiry into the actual properties of night soil and 

 other putrefactive substances, shewed me that the odour 

 of the fa'tid emanations from night soil by no means 

 depended on sulphurettpd carburetted or phosphuretted 

 hydrogene as Avas at that time generally believed but 

 that it really was caused by volatile animal matter in 

 a state of change, and that the foetor still continued 

 after all traces of sulphuretted hydrogen and ammonra 

 had been removed. 



In the experiments a quantity of night soil, previous 

 ly mixed with water, was introduced into a large retort, 

 and subjected to distillation, at a temperature not ex- 

 ceeding 120 Fah. At the commencemfnt of the distilla- 

 tion, paper smeared with carbonate of lead indicated, 

 by slight browning traces of sulphurated hydrogen, but 

 after a very short time the whole of the sulphurated 

 hydrogen was expelled, and all action on the prepared' 

 paper. The liquid obtained by this slow distillation 

 was clear, and colourless, with an insufferable odour of 

 night soil. To make sure that sulphuretted hydrogen 

 was not the cause of the bad odour, liquid was poured 

 on carbonate of potash in a retort and subjected to a 

 second distillation, with a little if any change of odour; 

 nor did the addition of a salt of lead produce a black 

 precipitate in the distillate. The complete absence of 

 sulphuretted hydrogen from the liquid was thus clearly 

 established. As it was evident that this liquid contain- 

 ed free ammonia, it was subjected to a third distillation 

 with a little diluted sulphuric acid, by which the whole 

 of the ammonia was retained, yet the original foetid 

 odour continued to be emitted from the fluid silthough 

 not quite so powerfully as before the removal of the 

 ammonia. However a portion of this third distillate, 

 preserved in a close vessel for some days regained its 

 original f(jctidity with the production of ammonia, and 

 a small white deposit. This liquid, on the addition of 

 nitric acid assumed a beautiful rose colour, which on 



