
PRODUCTS OF DECOMPOSITION OF COMENIC ACID. 235 
gas be passed through it for some time, the whole of the colour disappears, or the 
liquid only retains the faint yellowish-green characteristic of an aqueous solution 
of chlorine, without the formation of an immediate precipitate. After the lapse 
of some hours, groups of long, colourless, prismatic needles are deposited, the 
quantity of which is increased by the addition of hydrochloric acid. The mother 
liquor, on gentle evaporation, gradually acquires a brownish shade of colour, 
which passes ultimately into a very dark brown, and there deposited a further 
quantity of the new acid in prismatic crystals, separate and in groups, of a brown, 
nearly black, lustrous appearance. In this second mother liquor, in addition to 
the colouring matter, oxalic acid is to be detected. The colourless crystals at first 
obtained, after washing with cold water, were recrystallized from boiling water, in 
which they are readily soluble: they acquired, in this process, a slight shade of 
yellow, and presented themselves in the form of short, thick, square prisms. 
They gave the following results on analysis :— 



5-240 grains dried at 212° Fahr. gave 
7-210... carbonic acid, and 
0-847... water. 
3°877 grains dried at 212° Fahr. gave, after burning with lime, 
2:940 ... chloride of silver. 
Experiment. Calculation. 
—— 
Carbon, . «87:58 87°79 Cr 72 
Hydrogen, : 1:79 1-57 H, 3 
Oxygen, . : stn 42:01 oF 80 
Chlorine, . : 18-77 18-63 Cl 35:5 
100-00 100-00 190°5 
The above shews this substance to be an acid, obtained by the substitution of 
an equivalent of hydrogen in comenic acid, by an equivalent of chlorine, accord- 
ing to the following equation :— 
2 HO, C,, H, 0, +2C1=2 HO, ¢,, la 
Cl 
It crystallizes with three equivalents of water, which are readily expelled at 212° 
Fahr., as the following experiment proves :— 
10:528 grains air-dried substance lost at 212° Fahr. 
1-313... water, 
\ 0, + HCl. 
giving for per-centage 12°47, the number 12°41 being that corresponding to the 
formula 
H 
210, C,, {a } 0, +3.aq- 
This acid, as before mentioned, is readily soluble in hot water, less so in cold, 
but under both circumstances its solubility is much greater than that of the parent 
acid; it is very soluble in alcohol when warm. It imparts to persalts of iron the 
same deep red colour as meconic and comenic acids. When a piece of granulated 
zinc is placed in its aqueous solution, hydrogen is slowly evolved, and both zinc 
