180 RESEAECHES UPON THE CHEMICAL PEOPBRTIES OF GASES. 



green vitriol solution and milk of lime. The latter method for the removal of oxy- 

 gen is to be preferred, although the action is much slower. 



Palladium oxidized by heating in air is quickly reduced by free hydrogen. 



If a gas containing hydrogen is conducted over palladium oxide and then 

 through a narrow tube containing a very small quantity of a mixture of potassium 

 ferricyanide and green vitriol in fine powder, the moisture, foi'med in the reaction 

 between the hydrogen and the palladium oxide, will change the color of the powder 

 to blue. 



Silver oxide is reduced by hydrogen at 100° (Darvidowa, Ber., 1888, p. 442, E). 



Iodic acid is not reduced by hydrogen at 250°, i. e., at a temperature approach- 

 ing the point at which iodic acid dissociates (distinction between hydrogen and car- 

 bon monoxide). 



Iridium dioxide undergoes a reduction to metal in contact with free hydi-ogen. 

 The reduction occurs in the cold and is attended with brilliant scintillations. 



By employing a moisture indicator it is possible, by the help of this reagent, to 

 recognize minute quantities of hydrogen. 



In point of delicacy the palladium chloride reaction is superior to all others. 

 Exj^eriments are in hand with a view to the utilization of this reaction for the quan- 

 titative determination of hydrogen. 



The occlusion of hydrogen by the reduced palladium and consequent loss have, 

 so far, prevented the use of this reaction for quantitative work. 



METHANE. 



Preparation. — From methyl iodide by the method of Gladstone and Tribe (see 

 p. 157). 



Methane, the typical member of the paraffin group, is (with the possible excep- 

 tion of ethane) the most stable towards reagents of all hydrocarbons. 



1. Heactions in Solution. 



REAGENT. REACTIONS. 



Palladium chloride 



Platinum chloride 



Gold chloride 



Silver nitrate 



Ammoniacal silver nitrate 



Iridium chloride 



Rhodium chloride , 



Cerium dioxide dissolved iu sulphuric acid 



Potassium bichromate acidulated with sulphuric acid.. 



Mercuric chloride 



Ferric chloride 



Ruthenium chloride 



The solutions of these salts are unaltered by prolonged 

 contact with methane, cold or at 100°. 



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