RESBAKCHES UPON THE CHEMICAL PROPERTIES OF GASES. 181 



Potassium permanganate (2 per cent, solution) is unchanged whether neutral 

 or acidulated by sulphuric acid. 



Osmic acid is not reduced by methane in the cold. 



Potassium ferricyanide is unchanged. 



Peroxide of hydrogen mixed with lime water remains clear, proving that no 

 oxidation to carbon dioxide occurs. 



Calcium hypobromite solution remains free from any deposit of calcium car- 

 bonate. 



Bromine water is not discolored after prolonged contact. 



Chlorine attacks methane only at a temperature considerably above 100°. A 

 mixture of methane and chlorine was exposed over water to bright sunlight on a 

 July day without undergoing any noticeable "contraction in volume or change of 

 color (see experiments in " Chlorination of Methane "). 



Potassium rutheniate is slowly reduced with separation of metallic ruthenium. 



If methane is conducted into strong sulphuric acid to which crystals of perman- 

 ganate have been added, immediate oxidation to carbon dioxide occurs, as proved by 

 the action upon lime water (in this experiment stoppers made of plaster of Paris 

 were used). This reaction towards permanganic anhydride is a very delicate one. 

 All hydrocarbon gases yield a similar result. 



2. Reactions at High Temperatures. 



Ferric oxide (prepared by ignition of ferric nitrate) heated in a glass tube over 

 a strong Bunsen burner flame underwent very slow and incomplete reduction, some 

 carbon monoxide being formed in addition to carbon dioxide. Iodic acid (crystals) 

 is not reduced by methane on heating nearly to its temperature of dissociation (250°). 

 No iodine vapors and no carbon dioxide is formed. The action of methane upon the 

 chloride, bromide and iodide of silver was tried by the same method followed in the 

 case of hydrogen — these substances contained in a glass tube being heated in 

 methane and the gas then conducted into silver nitrate solution. The temperatures 

 of decomposition were as follows : 



TEMPERATtTBE OP DECOMPOSITION. 



Silver chloride At melting point of Ba (0103)3 (414°). 



Silver bromide Above melting point of Til (439"^). 



Silver iodide Slightly volatile without reduction. 



The order of reducibility by hydrogen and by methane is the same, therefore, as 

 in the case of the action of light, the chloride being the most easily reduced, the 

 iodide the most stable. 



A. p. s. — VOL. xvn. X. 



