166 Mr. J. F. Brown on some Salts and Products of 



which passed through ceased to precipitate nitrate of silver, and 

 then subjected to analysis in the usual way. 



6"53 grains substance gave 1*32 peroxide of iron. 



The per-centage calculated from the number is 20'21, while 

 20-56 is that coiTCsponding to the formula Fe^ 0^ 3C^^ H^ 0^. 



Products of decomposition of Pyromeconic Acid. — If some 

 crystals of the acid be moistened with strong nitric acid in the 

 cold, they immediately assume a white gelatinous appearance, 

 and bubbles of nitrous acid are soon evolved ; by the application 

 of a gentle heat the action becomes excessively violent, and con- 

 tinues so even though the heat be withdrawn, with the produc- 

 tion of oxalic and hydrocyanic acids. Sulphuric acid in the cold 

 has no action on pyromeconic acid ; but when gently warmed, it 

 dissolves it to a colourless fluid, which upon cooling deposits the 

 pyromeconic acid again. 



Several experiments were made by passing chlorine into a 

 solution of pyromeconic acid with the view of obtaining a chlo- 

 rine substitution compound, but without success, that reagent 

 acting too powerfully on it. Complete decomposition always 

 ensued, and oxalic acid was detected in the fluid, but not in 

 large quantity. I may here mention that I failed in obtaining 

 an Bether of pyromeconic acid by passing dry hydrochloric acid 

 gas into a solution of the acid in absolute alcohol, the crystals 

 which deposited from the fluid proving on analysis to be the acid 

 unaltered. 



Action of Bromine on Pyromeconic Acid. — When bromine 

 water is added to a strong aqueous solution of pyromeconic acid, 

 leaving the latter in excess, it is rapidly absorbed, yielding a 

 colourless fluid, which after standing for an hour or even less, 

 deposits the new acid in beautiful small colourless prisms. In 

 one experiment a large excess of bromine failed to yield any of 

 the new acid, even after standing a considerable time; more 

 bromine was then added, but no crystals made their appearance. 

 The solution, which had acquired a yellowish colour, was evapo- 

 rated to a small bulk, still without the formation of any bromo- 

 pyromeconic acid. It had now become perfectly black, and 

 oxalic acid was found in fluid. 



The crystals obtained by the action of a limited quantity of 

 bromine, after thorough washing with cold water, gave the fol- 

 lowing results on analysis : — 



4-97 grains substance gave 5*82 carbonic acid and 0*925 water. 

 4"845 grains substance gave, when burned with lime, 4"71 grs. 

 bromide of silver. 



