RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 151 



I. OXIDATION TEMPERATUEES. 



Preparation of Palladium Asbestos. — Long-fibred asbestos, washed by 

 hydrochloric acid, dried and weighed, was moistened with palladium chloride solu- 

 tion. Alcohol was dropped on the asbestos and ignited. After burning off the 

 alcohol a few times, the asbestos Avas heated in a Bunsen burner flame, and the treat- 

 ment with palladium chloride and alcohol repeated. With care, it is possible to 

 obtain a fairly uniform coating of palladium, although the metal tends somewhat to 

 collect on the surface of the fibres. Asbestos fibre, containing an amount of palla- 

 dium equal to 6 per cent, of the total asbestos plus palladium, was used in the fol- 

 lowing experiments : 



About 0.3 gm. of this asbestos was placed in a glass tube of one-eighth-inch 

 bore. This tube was then heated in an iron oven, having its lower portion filled up 

 to the level of the glass tube with iron turnings, so that the glass tube rested on and 

 was partly covered by the turnings. A thermometer was inserted into the turnings. 

 In some of the experiments the appai'atus described on p. 154 was used. In the Be- 

 richte der d. chem. Ges., 1879, pp. 636 and 1006, two articles appeared by W. Hempel 

 on the determination of hydrogen in gas mixtures by means of palladium sponge. 

 In the former article it is proposed to remove the hydrogen by occlusion : in the 

 latter, by oxidation. Winkler, in his Technical Gas Analysis (p. 81), employs palla- 

 dium asbestos for oxidation and determination of hydrogen in presence of methane 

 (and other paraffins), in water gas, coal gas, etc. In order to study the limits and 

 possibilities of these methods, and their applicability to various gas mixtures, the 

 following experiments were made: 



1. Hydrogen. — Hydrogen is not easily obtained pure ; all authors who have 

 had occasion to study its properties agree upon this. The purest zinc contains car- 

 bon, and hydrogen made by the action of sulphuric acid upon this metal is contami- 

 nated by traces of hydrocarbons. Other metals have been tried. Aluminium was 

 dissolved in sulphuric acid and also in caustic soda solution ; magnesium and cad- 

 mium were dissolved in hydrochloric acid ; sodium and potassium in water. In every 

 case, however, the hydrogen evolved contains hydrocarbons, as was shown by the 

 production of carbon dioxide on burning. After various trials, the following plan 

 has been found to give satisfactory results : The purest zinc obtainable (such as is 

 sold in sticks for use in Marsh's test for arsenic) was dissolved in dilute sulphuric 

 acid. The gas was passed (1) through a 6 per cent, solution of permanganate of 



