210 
Mr. Chenevix's Analysis of 
First, when an alkaline carbonate is used, the precipitate is 
a carbonate of hydrate of copper ; and this substance is soluble 
in an excess of the precipitant. I once evaporated some very 
beautiful blue liquor, obtained in an operation of this kind, and 
found a crystallized salt, which I became desirous to examine. 
But, as the solution contained another salt, formed by the acid 
(which originally held the copper in solution) and the alkali 
employed, I found it necessary to form some hydrate of copper 
directly for the purpose. 
Some hydrate of copper was therefore prepared, by decom- 
posing the nitrate of that metal by a very dilute solution of pot- 
ash, and well washing and drying the precipitate : it was that 
fine powder formerly well known as the oxide of copper. Some 
of this substance was thrown into a solution of carbonate of 
potash, through which a current of carbonic acid had been made 
to pass for a long time, and they were then slightly heated 
together. One part of the hydrate became of the same colour 
as the real oxide ; the other was dissolved, and the liquor was 
converted into a greenish blue solution. Thus, one part of the 
hydrate had yielded its water to the other, in order to favour 
this quadruple, or rather this double combination, of carbonate 
of potash and hydrate of copper : the liquor, when reduced,, 
afforded a mass, which, repeatedly redissolved and evaporated, 
with difficulty assumed any determinate form of crystallization. 
This salt is a carbonate of potash, holding a little copper. It 
is of a pale blue, and varies in colour, according to the quan- 
tity of water of crystallization, and of metal. It is slightly 
deliquescent, and soluble in about three parts of water, at 6o°, but 
requires much less water, when the water is boiling. It crystal- 
lizes by cooling, much like carbonate of potash. It is soluble 
