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LIV. Tlw Union of Hydrogen with Oxygen at Low Pressures 

 caused by the Heating of Platinum. By the Rev. P. J. 

 Kirkb y, Fellow of JSew College, Oxford*. 



DURING some experiments on the action of a platinum 

 wire upon a mixture o£ hydrogen and oxygen at 

 low pressures, I could detect no effect if the wire was 

 left alone. But by heating the wire with electric currents, 

 the gases were readily induced to combine. The rate of 

 combination increased with the temperature of the wire. 

 The combination was gradual, continued as long as the wire 

 was kept heated by the current and ceased directly the current 

 was broken. It followed that the platinum wire when raised 

 to a certain temperature must just begin to set up the 

 chemical reaction in the gas. To determine that temperature 

 for various pressures of the mixed gas was the primary object 

 of this investigation. 



The first set of experiments, then, described below were 

 made for the purpose of finding to what temperature a pure 

 platinum wire, placed in a mixture of hydrogen and oxygen 

 at a low pressure and in chemically equivalent volumes, must 

 be heated in order to initiate the chemical union of the 

 gases. 



The method adopted was the following ; — The hydrogen and 

 oxygen in the equivalent proportions of two volumes to one 

 were simultaneously generated in the same vessel by the 

 electrolysis of pure barium hydrate. The mixed gases were 

 dried and then introduced into the apparatus illustrated in 

 fig. 1. This was in connexion with two McLeod gauges, by 

 means of which any pressure below 40 mm. could be deter- 

 mined accurately. 



Fig. 1. 



A B 



The apparatus of fig. 1 was made from glass tubing about 

 33 cm. long and about 2 cm. in diameter. Platinum pieces 

 were fused into the glass at A, B. A thin platinum wire, 

 LM, about 20 cms. long had its ends carefully twisted round 

 two other pieces of platinum, PL, QM, so as to make a good 

 electric contact; for the wire was too thin to solder without 

 injuring it. The ends P, Q were then hooked onto the pieces 

 at A, h, and a soldering rod was passed up the glass tube and 

 united the ends of the platinum pieces at P, Q. The wire 



* Communicated by the Author. 



2K2 



