4 
Proceedings of the Royal Society of Edinburgh. [Sess. 
II. — The Preparation and Properties of Basic Copper Nitrate and 
the Hydrates of Copper Nitrate. By Alexander Charles 
Cumming and Alexander Gemmell. 
(MS. received November 9, 1911. Read December 4, 1911.) 
Anhydrous copper nitrate has never been prepared, though two 
hydrates are well known. The reaction between copper oxide and nitric 
acid would ordinarily be described by the equation : — 
CuO + 2HN0 3 = Cu(N0 3 ) 2 + H 2 0. 
The substance actually formed is a hydrate of copper nitrate, and the question 
arises as to the source of the water if nitric acid is used, which approximates 
to 100 per cent. acid. The above equation cannot possibly be a correct repre- 
sentation of the reaction in such a case. Examination of this and similar 
points appeared desirable. As much of the work on the chemistry of copper 
nitrate dates back to an early period, little has been done to it from a physico- 
chemical standpoint, and some experiments have therefore been made on 
the condition for the formation of the hydrates and their range of stability. 
Preliminary experiments confirmed the statement of previous observers 
that the hexahydrate was obtained by the action of dilute nitric acid on 
copper oxide and crystallisation below 25°, but that the trihydrate was 
obtained if the crystallisation was conducted above 25°, or if concentrated 
nitric acid was used. We found that the easiest method for the prepara- 
tion of the trihydrate was to obtain it from copper oxide and concentrated 
nitric acid, and recrystallise it from nitric acid. The trihydrate is readily 
soluble in hot concentrated nitric acid, but sparingly soluble in the cold 
acid. The crystals were then dried on a porous tile in a vacuum desiccator 
over solid potash. 
Non-existence of Graham's Basic Nitrate. — Graham ( Annalen der 
Pharmacie, 1839, 29, 13) states that if the nitric acid is above 1*4 specific 
gravity, a basic nitrate is obtained. The composition is not given, but the 
substance is said to be a green powder which is insoluble in water. That 
a basic nitrate should be obtained by the use of concentrated acid seemed 
remarkable and worthy of further investigation. We found by experiment 
that ordinary concentrated nitric acid (specific gravity 1*43) and fuming 
nitric acid (specific gravity P51) both acted on copper oxide to yield the 
trihydrate. No evidence conld be found of the existence of Graham’s basic 
