OXALATES, NITRATES, PHOSPHATES, SULPHATES, AND CHLORIDES. 73 
the heat of summer, the crystals became opake and of a talky lustre, without being 
disintegrated, and their proportion of water was reduced to two atoms. 
6. Double Chloride of Copper and Ammonium. 
Nil 1 Cl + Cu Cl H 2 . 
Hydrated chloride of copper dissolved with chloride of ammonium, in the propor- 
tion of eleven of the first to seven of the last, readily affords a double salt, in which 
we appear to have an atom of chloride of ammonium with an atom of the hydrated 
chloride of copper attached. This double salt is less soluble than the chloride of 
copper itself, and retains more strongly the two constitutional atoms of water of that 
salt ; illustrating in both of these points what appear to be two very general occur- 
rences : namely, 1 st, the reduced solubility of double salts ; and, 2nd, the closer 
attachment which constitutional water exhibits for a salt when that salt itself enters 
into combination. 
Analysis. Theory of NH 4 Cl + CuClH : . 
Chlorine 51 -03 51 -08 
Copper 23-35 22‘83 
Ammonium (N H 4 ) . 13-20 13-10 
Water ...... 12-09 12-99 
100-67 100- 
The water cannot be entirely expelled without risking the sublimation of chloride of 
ammonium, and hence the quantity of water obtained is under the truth. The cop- 
per is above the truth, from having been precipitated by caustic potash in the state 
of oxide, which last when so obtained always retains a little potash. 
There is a corresponding chloride of copper and potassium, but I did not succeed 
in forming analogous double salts with chloride of magnesium or with any other 
chloride of the class in the place of the chloride of copper. 
The chlorides have probably their analogues in the cyanides, but with the single 
cyanides of iron, copper, &c., we are less acquainted. It is worthy of remark, how- 
ever, that the disposition of the protocyanide of iron and of the cyanide of copper to 
combine with two atoms of cyanide of potassium may depend upon the cyanides of 
iron and of copper possessing two atoms of constitutional water, (like the correspond- 
ing chlorides,) which are displaced by two atoms of the alkaline cyanide in the for- 
mation of the double cyanides. In “ ferrocyanic acid” we have the protocyanide of 
iron combined with two atoms of hydrocyanic acid, in the place of the same two 
atoms of water. 
MDCCCXXXVII. 
L 
