154 EESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 



'No change occurred till the gold asbestos was strongly heated over flame, and even 

 then the oxidation was exceedingly slow, so that repeated passages of the gas were 

 required to produce complete oxidation. In the preceding experiment a Hempel's 

 apparatus was used. 



Expt. 4. Platinum Asbestos. — 



Air 90 



Hj'drogen 10 



The results Avere scarcely distinguishable from those obtained with palladium asbes- 

 tos. Palladium causes oxidation with somewhat greater intensity and at lower 

 temperatures. Determinations of hydrogen in mixtures of known proportions, using 

 a Hempel apparatus, gave very correct results. 

 Expt. 5. Iridium Asbestos. — 



Air 90 



Hydrogen 10 



When used in a Hempel apparatus in the cold or at 100° C, iridium seemed to have 

 very little influence, causing only a slight contraction in volume, even after the gas 

 had passed the iridium many times. 

 Expt. 6. — 



Air 90 



Hydrogen 10 



Palladium asbestos was moistened with a solution of carbonate of potash and dried 

 at a heat which was insufficient to cause fusion or sinteriug. In several trials the 

 alkali was found to seriously retard oxidation of the hydrogen, which was not fully 

 burnt until the gas mixture had been repeatedly (in one case ten times) passed 

 through the tube at 100°. 



HTDROC ARSONS. 



Description of Apparatus. — A, is an iron gas pipe, six inches in diameter and 

 thirty-four inches long, closed at both ends by heavy asbestos board. Four iron 

 pipes of three-sixteenths-inch bore are placed in the centre, passing through the 

 asbestos ends, and giving the apparatus the appearance of a boiler with four flues. 



B, B, are two side necks of one-half-inch pipe. The whole interior space around 

 the four small iron pipes is filled with iron turnings. Glass tubes of one-eighth- 

 inch bore, containing the metal-coated asbestos or other reagent, could be pushed 

 through the small iron pipes. Thermometers were placed in the side necks B, B. 

 Supposing the arrow to represent the direction of flow of the gas current through 

 the gas tubes, the metal-coated asbestos was, in the experiments, placed at the 



