198 RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 



Silver nitrate Voluminous, brownish black precipitate. 



Ammoniacal silver nitrate Prompt precipitation. 



Cadmium chloride Precipitation is slow and incomplete. 



Cadmium chloride in excess of ammonia Rapid and complete precipitation; bright yellow. 



Arsenious chloride Yellow precipitate, forming very slowly. 



Potassium permanganate acidulated by hydrochloric Rapidly bleached. The solution then precipitates ba- 

 acid. rium chloride, so that oxidation to sulphuric acid 



has occurred. No separation of sulphur is observed. 



Lead acetate Black precipitate. 



Bromine water Prompt oxidation to sulphuric acid. No sulphur is 



separated. 



Mercuric nitrate Turns milky white and darkens gradually to black. 



Nickel hydrate in water Darkens slowly to black. 



Ferric chloride Decided but incomplete reduction to ferrous chloride. 



Potassium ferricyanide Traces of reduction to ferrocyanide. 



Osmic acid Rapidly reduced. 



Potassium rulheniate Rapidly blackened. 



Cerium dioxide in dilute sulphuric acid Rapidly bleached. 



-^ These are all unchanged if dry. Sealed in a glass tube 



Yellow oxide of mercury l " , , , 



filled with the gas for two months, no change had . 



Litharge 



V occurred. If spread upon cotton, these substances 



Precipitated carbonate of copper , , -, , •, ^ 



I may be used to remove sulphuretted hydrogen from 



White lead 



■' a mixture of the two gases. 



Silver foil Is unattacked if dry ; under water it is quickly black- 

 ened. 



Comments. — Carbon oxysnlphide, by reason of its read}'^ change in presence of 

 water into hydrogen sulphide and carbon dioxide, gives, in the main, tlie reactions 

 of hydrogen sulphide, so that by the reagents usually employed for the detection 

 of the latter gas these two sulphur compounds are not distinguishable. In fact, 

 towards ammoniacal cadmium chloride solution, silver nitrate and palladium chlo- 

 ride, its reactions are characterized by somewhat greater promptness than in the 

 case of hydrogen sulphide. It is to be noted that, should H_S and CSO occur in a gas 

 mixture, the CSO would, by ordinary analytical methods, be mistaken for HjS, and 

 equal volumes of the two gases would yield the same weight of Ag.S, CdS, CuS, etc. 



The principal metallic sulphides as usually formed by H^S could be, in many 

 cases, more rapidly produced by CSO ; and, so far as I have been able to observe 

 the reactions, there is little or no tendency to separation of free sulphur such as is 

 common in precipitations by H2S. The absorption of CSO in ammoniacal cadmium 

 solution is so complete that on passing the gas through this solution none will escape 

 unabsorbed to cause precipitation in a second solution. An analysis seemed desira- 

 ble in the case of the silver compound obtained when CSO was passed thi'ough a 

 solution of ammoniacal silver nitrate, as the precipitate appeared much moi-e tloc- 

 culent and of a more brownish color tlian ordinary precipitated silver sulphide. 



