1911-12.] Preparation and Properties of Basic Copper Nitrate. 5 
salt. It was noticed that the solution of the trihydrate in nitric acid had a 
vivid green colour, but the salt which crystallised from this solution was 
the blue trihydrate. It seemed so improbable that Graham should mistake 
the blue-coloured trihydrate for a basic salt, that we have tried experiments 
under as varied conditions as possible in the hope of reproducing his result, 
but without success. When copper oxide interacted with a relatively small 
quantity of fuming nitric acid the mixture became very hot, but not hot 
enough to decompose the trihydrate unless external heat was also supplied. 
In one experiment in which commercial copper oxide was employed a small 
amount of an insoluble basic salt was obtained, but it was found to be due 
to manganese, which was present as an impurity in the copper oxide. 
The Interaction between Copper Oxide and Nitric Acid . — The substance 
obtained by the interaction of pure copper oxide and fuming nitric acid 
(specific gravity 1*51) was analysed after it had been dried on a tile in a 
desiccator over potash : — 
0*886 grms. of substance left on ignition 0*2915 grms. of copper oxide. 
Cu = 26 "2 per cent. 
0*217 grms. of substance gave by Crum’s nitrometer method 42*0 c.c. 
of nitric oxide measured at 760 mm. and 120°. 
N = 1 1*6 per cent. 
Calculated for Cu(N0 3 ) 2 , 3H 2 0. 
Cu = 26*2 per cent., N = 1T6 per cent. 
Attention may be drawn to the fact that the trihydrate can only obtain 
its water of crystallisation by the decomposition of nitric acid, if the acid 
approximates to 100 per cent., nitric acid. The reaction is attended by the 
copious evolution of nitrogen peroxide fumes, resulting from this decomposi- 
tion. The simplest formulation for this reaction would be 
Cu0 + 6HN0 3 = Cu(N0 3 ) 2 , 3H 2 0 + 2N 2 0 6 , 
accompanied by a further decomposition of the nitrogen peroxide into 
nitrogen peroxide and oxygen. 
The formation of copper nitrate trihydrate with copious evolution of 
nitrogen peroxide cannot well be explained in any manner other than the 
above, but to place the matter beyond question the presence of oxygen was 
proved in a special experiment. The nitric acid used was prepared by dis- 
tillation of a mixture of fuming nitric acid (specific gravity 1*51) and con- 
centrated sulphuric acid in a current of carbon dioxide. This has been 
shown by Roscoe ( Annalen , 116, 211 (I860)) to yield nitric acid which is 
very nearly anhydrous, and to contain only traces of nitrous acid. The 
