264 



MB. V. H. VELEY ON THE CONDITIONS OF THE 



From these observations it appears that the rate of evolution of carbonic oxide is 

 much accelerated by the presence of the graphite, for even after twenty-three 

 observations, corresponding to a loss in mass of nearly 14 per cent., the rate was 

 quicker than that observed before the addition of the graphite. At the conclusion 

 of the experiment the graphite was found to be uniformly distributed throughout 

 the acid liquid, and there was no perceptible odour of sulphurous oxide, thus 

 indicating that no reduction of the sulphuric acid had occurred. 



Effect of Silica. 



The experiment above was repeated with silica, obtained by decomposition of 

 silicon fluoride with water, which had been dried and recently ignited ; it was in 

 the usual form of a fine fluffy powder. 



Variation of temperature 80 0> 4-80 0< 6. 



On adding the silica and agitating the flask containing the decomposing mixture 

 an effervescence of gas took place, so tumultuous that some small quantity of liquid 

 frothed over; it was necessary to wait a few minutes until this had subsided 

 sufficiently to allow of observations being taken. 



