8 
Proceedings of the Royal Society of Edinburgh. [Sess. 
The formula Cu(N0 3 ) 2 * 2Cu(OH) 2 assigned by Graham to this substance 
appears therefore to be incorrect. 
The basic salt described above was prepared by heating the trihydrate 
to 100°. We found that decomposition of the trihydrate occurred even at 
room temperature under any conditions that led to the removal of water. 
For instance, when a current of dry air was passed through a tube packed 
with the trihydrate and then through caustic soda, a nitrogen compound 
could be detected within a few minutes in the soda. 
When copper nitrate trihydrate was kept in a vacuum desiccator over 
phosphorus pentoxide for some weeks, partial dehydration took place, and 
on opening the desiccator a strong smell of oxides of nitrogen was notice- 
able. In one experiment some trihydrate was kept for seven months over 
phosphorus pentoxide and weighed at intervals. The decomposition had 
not even in this time attained completion. The residue was analysed and 
found to contain 53*2 per cent, of copper and 9'5 per cent, of nitrogen. 
This does not agree with any simple formula, but indicates that the end- 
point would be a basic nitrate, and there is no reason to expect that it 
would differ from the basic salt prepared at a higher temperature. When 
solid potash was used as the dehydrating agent, a similar decomposition was 
found to take place. 
A basic nitrate was also prepared by boiling a concentrated copper 
nitrate solution with copper oxide, until in the course of twenty-four hours 
all the black copper oxide had been replaced by a green basic salt. This 
was collected, washed with hot water, dried, and analysed. One sample was 
air-dried on tile. 
0’283 grms. left on ignition 0T85 grms. of copper oxide. 
0T900 grms. gave 18*5 c.c. of nitric oxide at 760 mm. and 13°. 
Found 
Cu = 51*8 per cent., 17 = 5*87 per cent. 
A second sample was dried at 100°, and analysed. 
0*315 grms. left on ignition 0*210 grms. of copper oxide. 
0*1825 grms. gave 15*4 c.c. of nitric oxide, measured at 760 mm. 
and 13°. 
Found 
Cu = 53*l per cent., N = 5*26 per cent. 
Calculated for Cu(NO s ) 2 * 3Cu(OH) 2 , 
Cu = 53*0 per cent., N = 5*85 per cent. 
The basic nitrate prepared in this way is evidently identical with that 
prepared by heating the trihydrate. The same basic salt has been made in 
many ways and seems to be the only basic nitrate of copper. 
