112 



ping-power of H is rather lower than the value previously 

 given : but the exact determination depends on the value 

 adopted for the carbon atom, which is at present the subject 

 of investigation. 



The total ionisation in methane was found to be ri65 

 times greater than in air. Initial recombination effects were 

 small, probably less than in air : experiments on this point are 

 not yet complete. 



Preparation of the Methane. 



The gas was prepared by acting on an aluminium-mer- 

 cury couple with a mixture of methyl alcohol and methyl 

 iodide, following the directions of Bone and AVheeler (J.C.S., 

 Trans. 1902, 541). These authors freed the methane from the 

 hydrogen present as an impurity by passing the gases over 

 ''oxidized" palladium warmed to 100° C. Charitschkaff, how- 

 ever, states (J.C.S., A ii., 1903, 186) that when a mixture of 

 hydrogen and methane is passed over palladinized asbestos 

 not only does the hydrogen burn, but also some methane. 



In our experiment the gases issuing from the generator 

 were passed first through two vessels immersed in alcohol 

 which had been cooled to its freezing-point, roughly 160° T. 

 This cooling served to condense the vapours of iodide and 

 alcohol, and to remove also any higher hydrocarbons which might 

 have been formed. 



The mixture of methane and hydrogen passed secondly 

 through two vessels cooled in liquid air. In these vessels the 

 methane condensed to a colourless liquid, while the hydrogen 

 passed on and was neglected. 



After sufficient methane had liquefied, communication 

 between the first and second pair of cooling vessels was cut 

 off, and the methane allowed to evaporate into a mercury gas- 

 holder. The methane was then recondensed as far as pos- 

 sible by again cooling the vessels in liquid air. Part of the 

 methane was then allowed to evaporate into the gasholder, 

 and the gas coming off was pumped away. This partial eva- 

 poration was repeated, and a second portion of gas removed. 

 In this way the hydrogen remaining in the connecting tubes, 

 or dissolved in the methane, was removed. The methane 

 remaining showed a vapour 2^1'^ssure of about 150 mm. of 

 mercury. As far as can be slathered from the figures avail- 

 able, this pressure corresponds to that given by methane at 

 the temperature of liquid air, say 90° T. Evidently the 

 gas was quite pure. A determination of its density gave 

 the value *552, taking air as unity. This figure is almost 

 identical with the calculated value, which is '553. 



