INVOLUTION OF OASES FROM HOMOc KNK< H'S LIQUIDS. 



269 



The interval is reduced from a constant value of 4''5 to 3'' 80 by the introduction 

 of the pumice. 



Effect of Barium SulplwAe. 



The experiment was repeated with precipitated barium sulphate. In order to 

 determine whether the change of atmosphere above the fused salt had any effect upon 

 the rate of the decomposition, the cork, with the thermometer, was taken out, and 

 the superincumbent atmosphere of nitrous oxide, steam, and vapours of the salt was 

 completely blown away. But on restoring the cork the interval required for the 

 evolution of the 10 c.c. of the nitrous oxide was the same as before, which proves 

 that the results obtained in the cases investigated above are not due to the necessary 

 partial change of atmosphere in the process of introducing the finely-divided material. 

 The intervals of time required for the unit of decomposition obtained after the altera- 

 tion of the atmosphere are given in the second column. 



Variation of temperature, 191'5-191'8. 



The results show that the constant interval is reduced from 5'*45 to 1''85, or, prac- 

 tically, to one-third, by the introduction of such a chemically inert substance as 

 barium sulphate. 



Effect of Platinum Black. 



A sample of platinum black was prepared by reducing the chloride with a slightly 

 alkaline solution of sodium formate ; the precipitated metal was washed free from all 

 traces of chlorine and partially dried over sulphuric acid in a vacuum ; it was thought 



