RESEARCHES UPON THE CHEMICAL PROPERTIES OP GASES. 153 



rate of flow. The hydrogen by its rate of burning determines the temperature, and 

 the low specific heat of the palladium and feeble conductivity of the asbestos neces- 

 sarily increase the tendency to glow. Using air and hydrogen (5 : 1) repeatedly, no 

 explosion ever occurred, althongh the palladium often glowed with great intensity. 

 This is also true of palladium asbestos containing 30 per cent, of palladium, and 

 when the temperature was carried to 135° C. Air containing only 1 per cent, of 

 hydrogen may cause intense glowing of the palladium if the rate of flow is rapid. 

 Immersion of the tube in cold water will not prevent glowing. Caution is necessary, 

 should a mixture of oxygen and hydrogen be exposed to j)alladium. In experiments 

 made with tubes of one-millimeter bore, and at a temperature of 100°, it was found 

 that the hydrogen in burning causes a series of sharp explosions, very different from 

 the quiet and slow oxidation which invariably characterizes the mixture of air and 

 hydrogen. 



Expt. 2. — To determine the degree of completeness of the oxidation of hydrogen 

 by palladium asbestos. 



Air 90 



Hydrogen. 10 



The palladium tube was heated to 60°-70° C. G-as escaping from the palladium 

 tube was passed through oil of vitriol and phosphoric anhydride, in order to dry 

 thoroughly; then through a second (porcelain) tube containing palladium asbestos^ 

 and finally into a small weighed tube of phosphoric anhydride. The second palla- 

 dium tube was heated to intense redness. It was found that absolutely no moisture 

 was formed in the second contact with palladium, although 5 liters of the gas mix- 

 ture were used and the rate of flow varied from 40 to 100 bubbles per minute. It 

 was shown, moreover, that complete oxidation is independent of the glowing of the 

 palladium. 



Hence the oxidation of hydrogen by air in presence of palladium is complete at 

 a temperature of G0°-70° when the gas mixture is dry. Quantitative experiments, 

 to be detailed later, showed that in the case of air containing 0.2 of hydrogen a cor- 

 rect determination of the hydrogen was possible. The temperature in this case was 

 100° C. If the hydrogen and air mixture is moist, oxidation is easily and completely 

 attained at ordinary temperatures. 



Hydrogen is said to ignite at a temperature of 552° C. (Le Chatelier, Ball. Soc. 

 0/nm., ISSS, p. 2). 



Expt. 3. Gold Asbestos. — 



Air 90 



Hydrogen 10 



