262 



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



occurred at a temperature of 35 0t 8-35 0> 9. But some finely divided particles, afterwards 

 shown to be silica, were suspended in the solution of sodium formate ; these were, 

 doubtless, due to some process adopted by the manufacturer for obtaining the salt. 

 It was observed that these particles were continually being borne up by the bubbles 

 of gas, and seemed to serve as nuclei for their formation. 



The experiment was then repeated under conditions precisely the same, with the 

 exception that the solution of the sodium formate was Jittered into the sulphuric acid, 

 to free the solution from the coarser and visible particles. No appreciable quantity of 

 gas was given off at 35'8, and it was found necessary to raise the temperature about 

 38, viz., to 73'8, to obtain a rate of evolution of gas similar to that in the above 

 experiment. 



As these results appeared to be similar to those which Mr. HARCOURT had observed 

 in the decomposition of hydrogen peroxide, he conducted the two following experi- 

 ments. A mixture was made of 300 c.c. sulphuric acid (sp. gr = 17877) and 130 c.c. 

 of water ; to this, when cool, was added 10 c.c. of a filtered aqueous solution of sodium 

 formate (containing 1 gram of the salt). Of this mixture two portions of 200 c.c. 

 were taken, and introduced into two similar flasks, of which one contained a quantity 

 of well- washed, recently ignited pumice suspended in 10 c.c. of water, the other 10 c.c. 

 of pure water. The flasks, fitted with delivery tubes, were heated side by side in a 

 water bath, and the carbonic oxide gas collected in two graduated tubes, standing 

 in a pneumatic trough. The intervals of time between successive observations were 

 approximately equal ; the volumes collected in the two tubes were read simul- 

 taneously ; the temperature varied throughout the experiment from 75'8 to 76'2. 



The first observation includes the volume, probably about 4 c.c., given off in conse- 

 quence of the expansion of the liquid and of the enclosed air. 



The rate of evolution of gas from the mixture containing the pumice is to that 

 from the mixture without the pumice in approximately the ratio 5 : 2. 



