118 



obtained, it is in the form of beautiful large transparent plates, of 

 ready solubility in water and alcohol. It is also soluble in ether, 

 reddens litmus faintly, and is completely volatile at 212°, a property 

 which may serve as a test of its purity from paracomenic acid, that 

 acid requiring a much higher temperature for its sublimation. Se- 

 veral attempts were made to prepare the ammonia and potash salts of 

 this acid, but without success. 



The acid gave on analysis per-centage results agreeing with the 

 formula Cjq Hg Og + H O, which is that hitherto adopted. 



Pyromeconate of baryta, Ba 0, 0^^, Hg 0^ + H O, precipitates as 

 small colourless silky needles, when a warm ammoniacal solution of 

 pyromeconic acid is mixed with acetate of baryta. By evaporation 

 in vacuo, it crystallises in four-sided prisms of a yellow colour. It 

 is the most soluble in water of all the earthy salts of this acid, 100 

 parts of water at 60° dissolving 2-50 parts of the salt. 



Pyromeconate of strontia, Sr O, C^^ H^ 0^ + H 0. This salt may 

 be obtained by mixing alcoholic solutions of the acid with ammonia 

 and nitrate of strontia, when there ensues an immediate precipitate 

 of the salt in small colourless crystals, of sparing solubility in water 

 and alcohol, 100 parts of the former at 68° dissolving 1'3 parts. 



Pyromeconate of lime, Ca C^^ Hg Og + H 0. This salt was pre- 

 pared in a manner similar to that of the two preceding. It is 

 soluble in water and alcohol to a small extent, 100 parts of the for- 

 mer at 68°, dissolving 0*31 of the salt. 



Pyromeconate of magnesia, Mg O C^^ Hg O^, falls as an amor- 

 phous powder, when acetate of magnesia is added to an ammoniacal 

 solution of pyromeconic acid. 



The pyromeconates of lead, copper, and iron, have already been 

 examined, and I merely repeated their analysis, to confirm the for- 

 mulae which have been given for them. 



The products of decomposition of this acid were next examined, 

 cold nitric acid of sp. gr. 1*4 decomposes it with the evolution of 

 nitrous acid gas, and production of oxalic and hydrocyanic acids. 

 Sulphuric in the cold has no action on pyromeconic acid, but when 

 gently warmed, it dissolves to a colourless fluid, which, upon cool- 

 ing, deposits the acid again. I failed, however, in procuring an 

 ether or a chlorine substitution product of this acid. 



Bromopyromeconic acid, Cjq Hg Br Og + H 0, is obtained in 

 the form of beautiful small colourless prisms, when bromine water 



