Decomposition of Pyromeconic Acid. 167 



10000 100-00 189-26 



Which show that they consist of an acid produced by the sub- 

 stitution of an equivalent of hydrogen in pyromeconic acid by an 

 equivalent of bromine. 



This acid is of sparing solubility in cold water, more so in hot, 

 and reddens htmus slightly. Boiling alcohol dissolves it readily, 

 from which it crystallizes in beautiful fibrous plates ; and if the 

 cooling be carefully effected, in short prisms. It imparts to 

 persalts of iron a deep purple colom*, quite distinct from the red 

 produced by the original acid. Nitric acid decomposes it with 

 effervescence, but sulphm'ic dissolves it without any apparent 

 decomposition. Submitted to destructive distillation, it fuses 

 and then blackens, hydrobvomic acid being evolved in large 

 quantity ; after the continuation of the heat, a white crystalline 

 substance begins to collect on the cool part of the tube, but in 

 quantity too small to admit of examination. 



It gives no precipitate with nitrate of silver, neither when 

 boiled does it reduce the oxide to the metallic state. It causes 

 no precipitate in solutions of chloride of barium, calcium, or sul- 

 phate of magnesia, even in the presence of ammonia. Ammonio- 

 sulphate of copper, though producing no effect in the cold, gives 

 when heated a precipitate of a bluish tint. 



Bromo-pyromeconic acid, like pyromeconic, is monobasic, 

 forming only one series of salts. The salt employed for con- 

 troUing the analysis and establishing the saturating power of the 

 acid was that of lead. 



Bromo-pyromeconate of Lead. — A warm alcoholic solution of 

 the acid gives with acetate of lead, also dissolved in alcohol, a 

 white precipitate of small dense crystalline needles which rapidly 

 fall to the bottom of the vessel. From its insolubility in water 

 and alcohol, rccrystallization of the salt was impossible ; thorough 

 washing with alcohol was therefore resorted to. This salt may 

 also be obtained by using aqueous solutions of the acid and salt 

 of lead with the addition of ammonia, but the product is in this 

 case very much coloured. 



The lead in the following analysis was determined as sulphate 

 by ignition of the salt with sulphuric acid. It loses nothing 

 at 212°. 



