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phurized compounds, and also a practical process for their removal. 

 My attention was specially drawn to this subject by a conversation 

 with the manager of a London gas-works. He informed me that 

 he not unfrequently filled his gas-holders with gas which would not 

 affect acetate of lead, and that after the gas had been stored a few 

 hours, it became so foul as to blacken lead-paper the instant it was 

 applied. He sought an explanation of this phenomenon ; and as the 

 water of his gas-holder tanks was clean, and there were no accidental 

 sources of sulphide of hydrogen, I concluded that an organic com- 

 pound containing sulphur and hydrogen had been broken up, and 

 that the sulphide of hydrogen was thus produced. I learnt also, by 

 other observations, that gas which went to the gas-holders free from 

 ammonia, sometimes became ammoniacal if kept, and joining this 

 fact with the former one, inferred that the compound which thus 

 broke up contained nitrogen as well as sulphur and hydrogen. 

 Subsequently I observed that the saturated clay taken from the 

 purifiers of gas-works, contained a quantity of foul naphthalin. This 

 led me to procure a quantity of (so called) nuphthalin which had 

 been taken from the mains of a London gas-works, and which there- 

 fore must have been deposited by purified gas. Some portions of 

 this naphthalin were white, but others were slightly darkened by the 

 presence of carbonaceous matter, and the whole was in fyie powder, 

 aggregated together by the process of deposition. The tendency to 

 form exceedingly small crystals seems a constant characteristic of 

 naphthalin which has been deposited in gas-pipes, for by no amount 

 of care and trouble have I been able to obtain it in large crystals, 

 though the solutions from which it has crystallized have been 

 months in evaporating. With naphthalin from tar, on the contrary, 

 I have obtained, from an etherial solution, crystals an eighth of an 

 inch thick, nearly half an inch broad, and more than half an inch in 

 length. The supposed naphthalin from gas-pipes dissolves wholly 

 in ether and hot alcohol, and crystallizes from the spirit on cooling 

 as pure naphthalin does. The solutions are neutral to test-papers. 

 Boiled with an alcoholic solution of potash it evolves no ammonia, 

 and with hydrochloric acid no sulphide of hydrogen. Heated alone, 

 it evolves first ammonia, and then sulphide of ammonium, mixed, I 

 think, with a trace of bisulphide of carbon, and then distils. Several 

 samples began to give off their ammonia at 388 Fahr., and sulphide 



