706 
Proceedings of the Royal Society of Edinburgh. [Sess. 
In one experiment 350 grams of nitric anhydride were obtained. For 
the preparation of tartaric acid dinitrate a quantity of nitric anhydride 
slightly in excess of that required by the equation 
C 4 H 4 0 4 (0H) 2 + 2N 2 0 5 = C 4 H 4 0 4 (N0 3 ) 2 + 2HN0 3 
is mixed with finely powdered tartaric acid. The mixture is allowed to 
stand over solid caustic soda in an evacuated desiccator for some hours, 
till it is practically free from nitric acid. 
It is then treated with dry ether, which dissolves the dinitrate, but 
does not dissolve the unchanged tartaric acid. Most of the ether can 
be evaporated on the water bath, but the temperature of the solution 
should not be allowed to rise above 40° C. or decomposition may result. 
The last portions of ether are removed in vacuo over concentrated 
sulphuric acid. 
130 grams of the dinitrate were obtained in this way from 100 grams 
of tartaric acid. This is 81 per cent, of the theoretical yield. 
The following quantitative experiment was carried out in order to 
