
PRODUCTS OF DECOMPOSITION OF COMENIC ACID. 241 
dried, but soon commence to lose ammonia in a dry atmosphere. A portion of 
the substance which had been exposed one night was placed im vacuo over sul- 
phuric acid; it was found to lose less weight by about half a per cent. than would 
correspond to the ammonia in a salt of the composition. 
NH, 0, C, H, 0, C,, H; 0,,. 
As the residue was found to consist of pure comenovinic acid, there can be little 
doubt that the above is a true ammonia salt. 
Its other salts, with the alkalies and alkaline earths, are very soluble. Its 
silver salt is gelatinous, and rapidly decomposable even in the dark. 
Decomposition of Comenate of Ammonia. 
Comenamic Acid.—I mentioned, in a former part of this paper, that bicomenate 
of ammonia is decomposed, when subjected to a temperature of 390° Fahr. in a 
sealed tube. The contents of the tube were a black coaly mass, which partially 
dissolved in boiling water. The filtered solution gave, with hydrochloric acid, a 
white scaly precipitate, separating on cooling. I did not endeavour to procure 
more of this substance in this manner, as I considered it to be the comenamic 
acid, which a more convenient process enabled me to obtain in sufficient quantity. 
When a solution of comenate of ammonia, containing an excess of the alkali, 
is boiled, it soon becomes coloured, and after some little time a black-red fluid is 
obtained ; if the boiling be continued till the whole or the greater part of the 
excess of ammonia is expelled, and the fluid be then allowed to cool, a grey sedi- 
ment falls to the bottom of the vessel. This, when thrown upon a filter, is found 
to have a most peculiar, clayey, tenacious character ; it is the ammonia salt of co- . 
menamic acid, very impure, from adhering colouring matter. It dissolves, though 
sparingly, in boiling water; and hydrochloric acid added in just sufficient quan- 
tity to decompose it, precipitates very dark bronze-coloured scales of comenamic 
acid, which separate completely when the liquid cools. Excess of hydrochloric 
acid is to be avoided, as the new acid is extremely soluble in this reagent. The 
dark crystals are readily deprived of their colour by two or three crystallizations 
from boiling water, and very easily by the aid of animal charcoal, which must, 
however, for this purpose be entirely free from iron, as the least quantity of this 
substance imparts a purple colour to solutions containing the acid. 
When pure, comenamic acid presents itself in the form of brilliant colourless 
plates, the following is its analysis :— 
5-540 grains dried at 212° gave 
I. ¢ 9:°345 ... carbonic acid, and 
1685 ... water. 
5-585 grains dried at 212° gave 
Il. < 9-487 ... carbonic acid, and 
1-715 ... water. 
6:505 grains dried at 212° gave 
9500 ... platinum salt of ammonia. 
VOL. XX. PART I. 37 
