465 



down to a small bulk. The sulphate of lead being filtered off, 

 solution of potash was added, but no oxide of zinc appeared. 



" Thus it was proved that the celt did not contain zinc ; 

 other trials, however, showed that it contained a little lead. 

 In order to determine the proportions of the constituent 

 metals, the following method was adopted : I believe it is one 

 which diflFers in some respects from that hitherto practised, 

 but previous trials convinced me that in such cases it is 

 necessary. 



" 100 grains of celt metal were introduced into a tubula- 

 ted retort, to which were attached a receiver, and a series 

 of three very small Woulfe's bottles, each of which con- 

 tained a little liquid ammonia ; the receiver was empty. An 

 ounce and a-half measure of pure nitric acid being poured 

 through the tubulature of the retort, and a spirit lamp applied, 

 a violent effervescence ensued ; everything dissolved except 

 the tin, which became peroxidated. Some acid and much 

 nitrous gas came over, the latter of which passed through the 

 ammonia. When the celt metal had all disappeared, the con- 

 tents of the Woulfe's bottles were mixed with those of the re- 

 ceiver; the resulting liquor was of a light blue colour, for the 

 nitrous gas had carried over with it some copper ; it was 

 reserved for a future process. 



" The solution of nitrate of copper was diluted with dis- 

 tilled water, and introduced into a precipitating glass, in order 

 that the peroxide of tin should subside. When this happened, 

 the perfectly transparent solution of copper was decanted, and 

 the peroxide of tin was digested with a little nitric acid, in 

 order to dissolve away minute particles of copper, which some- 

 times escape solution by being entangled in the peroxide of 

 tin. The pero.xide was then well edulcorated with frequent 

 affusions of distilled water. The collected washings were 

 evaporated to one-eighth, and a minute quantity of peroxide 

 of tin was thus recovered, which was added to the rest. By 



