162 Mv. 3. F. BrowTi on some Salts and Products of 



which it crystallizes in four-sided prisms of considerable size. It 

 is sHghtly acid to litmus, and even after three crystaUizations 

 from boiUng water it retained its acidity. It is completely volatile 

 at 212°. A quantity having been exposed to that temperature for 

 about fom-teen hours, was found to have entirely disappeared. 

 This property may serve as a test of its purity from paracomenic 

 acid, with which pyi-omeconic, as first subUmed, is always conta- 

 minated, that acid requiring a much higher heat to volatilize it. It 

 gives, as is well known, a deep red colour with persalts of iron, 

 and does not precipitate chloride of calcium, barium, manganese, 

 nor sulphate of magnesia, either hot or cold, even on the addition 

 of a small quantity of ammonia. Bichloride of mercury gives 

 after some time a white amorphous precipitate, soluble on boiling 

 the fluid. When a hot aqueous solution of pyi-omeconic acid is 

 treated with strong caustic potash in excess, and allowed to stand 

 some hours, crystals soon begin to form, which upon examina- 

 tion proved to be the acid unaltered ; a similar experiment was 

 made with ammonia, but with the same result, the fluids in both 

 cases becoming nearly black. 



To ascertain the purity of the acid, the following analysis was 

 made of it, dried in vacuo, after one sublimation. 



5-74 grains substance gave 11*133 carbonic acid and 1*905 

 water. 



10000 100-00 112 



The formula of the acid is therefore represented by 

 C10H3 05 + HO. 



Pyromeconate of Baryta. — This salt may be obtained by 

 mixing a warm ammoniacal solution of pyromeconic acid with 

 acetate of baryta, when it makes its appearance after a short time 

 in small colourless silky needles. In dilute solutions they do 

 not appear immediately, but after standing some time they com- 

 mence forming and rapidly increase. It is the most soluble in 

 water of all the earthy salts of this acid, — 181-90 grains of a 

 saturated solution at 60° F. gave on evaporation at 212° a residue 

 of 4-50 grains = 2-50 per cent. It is of sparing solubility in 

 alcohol. Like the other pyromeconates, it reacts strongly alka- 

 line, and gives a slight red colovu- with chloride of iron, which 

 may be made much more apparent if the crystals be employed 

 instead of a solution of the salt. By evaporation in vacuo it 

 deposits itself in short prisms of a yellowish coloui-. When ex- 



