407 



tendency to solidify. At this period I connected the same 

 series of Woulfe's bottles, still containing the ammonia, which 

 had been used for condensing the nitrous vapour, and which 

 also held a little copper dissolved. Through this ammonia 

 the nitrous gas evolved from the nitrate of copper, now under- 

 going decomposition in the retort, was obliged to pass, pre- 

 viously to its emission into the atmosphere, in its passage 

 transferring to the ammonia the chief part of the copper which 

 it had carried over. The heat was gradually raised, and con- 

 tinued until the nitrate of copper was converted into a black 



mass. 



" I have mentioned that the chief part of the volatilized 

 copper was detained by the ammonia, but it was not entirely 

 absorbed, for, at the latter end of the decomposition of the 

 nitrate of copper, the flame of a spirit lamp, held in the fumes 

 which escaped from the issue-tube of the Woulfe's bottles, 

 assumed a splendid green colour. The loss in this way must 

 be trivial. 



" The bottom of the retort which contained the black 

 mass was now cut out by means of a red-hot tobacco pipe, 

 and the black matter detached from the glass. But so obsti- 

 nately did a very small portion adhere, that it could only be 

 removed by nitric acid ; the nitrate thus formed was decom- 

 posed by heat, and the resulting black matter was added to 

 the main product. 



" In order to recover the copper which was contained in 

 the Woulfe's bottles and receiver, the liquors were collected 

 and distilled to a very small bulk. The distilled liquor was 

 colourless, and, therefore, contained no copper. The residue, 

 being transferred into a capsule, was decomposed by heat, and 

 the very small quantity of black matter which resulted was 

 added to the main product. 



" The total quantity of black matter was now heated red- 

 hot, by means of a Russian furnace, for about five minutes. 

 Before it cooled, its weight was ascertained to be 106767 



