of Edinburgh, Session 1880-81. 
241 
3. Comenic Acid. By D. B. Dott. Communicated by 
Professor Crum Brown. 
In continuation of a short paper on meconic acid previously 
communicated to the Society, I submit the following notice of some 
of the salts of comenic acid. 
As is well known, comenic acid is formed from meconic acid by 
elimination of carbonic anhydride, according to the equation 
- C 7 H 4 0 7 = C 6 H 4 0 5 + C0 2 . This change may be effected by heat 
alone, but a better product is obtained by the action of boiling 
aqueous hydrochloric acid. It was by the latter method that the 
acid used in my experiments was prepared. Comenic acid is easily 
purified by crystallisation from boiling water, in which it is 
sparingly soluble, and by conversion into ammonium salt, which is 
likewise purified by recrystallisation. Comenate of ammonia forms 
long well-defined prisms, which are much less soluble in water than 
the corresponding salt of meconic acid. 
I have endeavoured to prepare most of the salts of comenic acid 
as described by How* and others, with results generally in accord- 
ance with their experiments. I have also succeeded in obtaining 
two crystalline comenates of silver, or rather the same salt crystal- 
lised in two different forms. The silver salts hitherto noticed were 
amorphous. 
Silver Salt. 
(1.) This was prepared by adding nitrate of silver to solution of 
ammonium comenate, the precipitate being dried in water-bath. 
8'205 grs. gave by ignition 3*190 grs. Ag = 38*87 per cent. 
(2.) Prepared by adding excess of nitrate of silver to solution of 
ammonium comenate. The air-dry precipitate dried in air-bath at 
120° C. 
10*78 grs. gave by ignition 4*44 grs. Ag = 41*18 per cent. 
5*04 grs. ,, 2*08 grs. Ag = 41*26 „ 
(3.) Nitrate of silver was mixed with solution of annnonic 
* 
Ed. Phil. Trans., xx. 2*25. 
