Union of Hydrogen and Oxygen at Low Pressures. 171 



other end of the torsion-rod. the deflexion was much less, as 

 was to be expected. 



We have also made some qualitative experiments with a 

 blackened glass cylinder — a ring cut from a test-tube — sus- 

 pended by a quartz fibre with its axis vertical. When a 

 beam fell on this in any direction not along a diameter, there 

 was always a twist in the direction corresponding to the 

 tangential stress. 



XVII. The Union of Hydrogen and Oxygen at Low Pressures 

 through the Passage of Electricity. By Rev. P. J. KlRKBY, 

 Fellow of New College, Oxford". 



IN the Phil. Mag. for Feb. 1901 I described some expe- 

 riments which exhibited the effect of passing electricity 

 with a luminous discharge through hydrogen and oxygen, 

 mixed in equivalent proportions and at low pressures. The 

 experiments showed that a partial union of the gases into 

 water-vapour is the result ; and that if the pressure and the 

 potential-difference of the plates during the discharge remain 

 steady, the quantity of water-vapour formed is proportional 

 to the quantity of electricity which has passed — in other 

 words, to the product of the current and the time. They 

 showed, moreover, that if Ap mm. is the fall of pressure 

 associated with the passage of AQ coulombs at the pressure 

 p mm. ; and if X is the voltage-difference of the plates during 

 the discharge, then, within the limits of experimental errors, 



1 Ap . , X 



~ ^r is a function or — 

 p AQ p 



The experiments described in the following paper were 

 undertaken with the view of deciding, lirst, how changes in 

 the distance between the parallel electrodes, between which 

 the discharge took place, would affect these results; and, 

 secondly, whether the same effects would be observed if non- 

 oxidizable plates were used. 



While the general arrangement of the apparatus was sub- 

 stantially unchanged, there were several alterations in detail. 

 A more satisfactory method of preparing hydrogen and 

 oxygen was adopted. The gases were prepared simultaneously 

 by the electrolysis of pure barium hydrate contained in a 

 small sealed glass vessel. By this method the gases are 

 generated tree from hydrocarbons and, according to Mr. H. 

 B. Baker, five also from ozone and peroxide of hydrogen 

 (Trans. Chein. Soc. xxxviii. 1\)()2). The mixed gases were 

 * Communicated bv the Author. 



