268 



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



The interval of time is suddenly reduced to about one-third by the introduction of 

 the silica, as in some previous cases, but the rate of the decomposition quickly 

 resumes its former course. 



Effect of Pumice. 

 This experiment was made with a similar mixture. Temperature, 58-59 0> l. 



The interval of time is here reduced from 8'"03 to 6''28 by the introduction of the 

 pumice ; otherwise the results are comparable with those of the former experiment. 



Decomposition of Ammonium Nitrate, into Nitrous Oxide and Steam. 



NH 4 NO 3 = 



20H. 



Owing to the solubility of nitrous oxide in water, the twin U-tube apparatus was 

 modified by the interposition between the flask and the U-tube of a bent tube, 

 provided with two bulbs at different levels, the form of which is described at length 

 in my paper " On the Rate of Decomposition of Ammonium Nitrate."* By its means 

 each measure of nitrous oxide was represented by the collection in the U-tube of its 

 corresponding volume of air. The manipulation and processes of purification of the 

 salt were the same as those adopted in the previous experiments. Such a quantity of 

 salt, about 200 grams, was taken that the loss of mass between any two consecutive 

 observations should be far too small to affect the results. 



Effect of Pumice. 



In this case the temperature of the pumice introduced was as nearly as possible 

 that of the fused salt, so as not to produce local solidification of the salt around the 

 pumice, and thus retard the decomposition. 



Temperature, 182'2-182 -.'). 



* ' Chem. Soc. Jonrn.,' 1883, p. 373. 



