12 
DE. W. A. BONE AND ME. E. V. WHEELEE ON THE COMBINATION OF 
to open the tap t in the corresponding “ bye-pass ” to shut up a sample of the gas at 
any given moment. At the conclusion of the experiment, after the rest of the 
apparatus had been exhausted, the contents of each sampling tube could be succes¬ 
sively withdrawn through the pump for analysis. # 
Preparation of the Gases. 
The electrolytic gas employed during the research was prepared by the method 
recommended by Mr. H. Brereton Baker, f namely, by the electrolysis of a solution 
of highly purified barium hydroxide. This method ensures its freedom from hydro¬ 
carbon impurity, ozone, or hydrogen peroxide, [and repeated careful analyses showed 
that its constituents were present in exactly their combining ratio.— February 10, 
1906.]. The gas was collected in a graduated glass holder, fitted with ground-glass 
joints, over a mixture of equal volumes of pure glycerine and water. From this holder 
the gas was passed direct into the circulation apparatus, as required. When it was 
necessary to experiment with mixtures originally containing an excess of one of the 
reacting gases, the electrolytic gas was mixed in the holder with a known proportion 
either of hydrogen, prepared electrolytically from a solution of barium hydroxide, or of 
oxygen, prepared by heating recrystallised potassium permanganate, j 
Experimental Method. 
Throughout a given series of experiments the gas supply of the furnace was never- 
interfered with, so that the combustion tube was kept at the desired constant 
temperature day and night, not only during each experiment, but also during the 
intervals between two experiments. In this way perfect uniformity of temperature 
conditions was secured. At the outset of an experiment, the circulation apparatus 
was thoroughly exhausted by bringing the auxiliary Sprengel pump into action. The 
experimental mixture was then admitted to the vacuous apparatus, and five minutes 
later the first pressure reading was taken. Subsequent pressure readings were taken 
at regular intervals up to the end of the experiment; these readings, corrected for 
small variations in the room temperature and for the pressure of water vapour, gave a 
direct measure of the reaction velocity. The time intervals were determined by a 
chronograph recording stop-watch. 
* [It should be stated that all the gas-analyses in connection with the research were carried out over 
mercury in an improved form of McLeod apparatus described by one of the authors in the ‘ Proceedings 
of the Chemical Society,’ vol. XIY. (1898), p. 154 .—February 10, 1906.] 
t ‘Journal of the Chemical Society,’ vol. LXXXI. (1902), p. 400. 
| The expression “ normal electrolytic gas,” used throughout this paper, means electrolytic gas without 
any addition of oxygen or hydrogen. 
