86 SCIENCE PROGRESS 



If it be desired to investigate the effect of a gas on the rate 

 at which chlorine and hydrogen interact, a given quantity 

 of the gas can be admitted to the insolation vessel by the 

 following procedure : The three-way taps b and d are turned 

 so that the tube z communicates only with the tube w and a 

 current of the gas to be used is passed in at z and out at w; 

 when all the electrolytic gas in the capillary tube between b and 

 d has been displaced, the three-way taps are turned so that the 

 tubes z and w are closed and the cell and actinometer are brought 

 into direct communication ; the gas contained in the capillary 

 tube between b and d is then driven into the insolation vessel 

 by means of a current of electrolytic gas. 



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