Products of the Distillation qfMeconic Acid. 131 



I. 0*421 grm. of the salt, dried at 212° F. and burned with 

 chromate of lead, gave 0*71 7 of carbonic acid and 0*092of water. 



4883-791 100-00 100*00 



It is evident from these analyses that the iron salt is neu- 

 tral, the atoms of acid being as three to two. It gives pre- 

 cisely the same formula, C ]0 H 3 O 5 , for anhydrous pyrome- 

 conic acid as the lead and copper salts; the atomic weight 

 found being 1299-7; the calculated, 1302. 



When oxide of silver is added to a cold solution of pyro- 

 meconate of silver, it immediately combines with the acid and 

 forms a bulky light-grayish compound, which is but slightly 

 soluble, and has very little permanence. It quickly decom- 

 poses even in the cold, becoming of a deep black colour. If 

 it is boiled in a glass tube the inner surface of the tube be- 

 comes coated with a mirror of metallic silver, as the oxide is 

 reduced without the evolution of any gas. This reaction 

 with oxide of silver, together with the red colour which the 

 acid strikes with a persalt of iron, form a very easy means of 

 detecting pyromeconic acid. 



When pyromeconic acid is added to a solution of nitrate 

 of silver no precipitate or change of colour appears, and it re- 

 quires to be boiled for some time before even a very partial 

 reduction of the oxide is effected. But if a few drops of am- 

 monia are first added to the nitrate of silver, the pyromeconic 

 acid immediately produces a bright yellow gelatinous preci- 

 pitate. This precipitate is pretty soluble both in cold water 

 and in alcohol, it also quickly changes its colour even in 

 vacuo, becoming dark brown, owing, I apprehend, to partial 

 decomposition. When strongly heated it deflagrates slightly ; 

 one portion gave 51*80 per cent, of oxide of silver, which ap- 

 proaches the calculated quantity in neutral pyromeconate of 

 silver, which is 52-70 per cent, of oxide. The examination of 

 this salt is attended with considerable difficulty, owing to its 

 little permanence. Pyromeconic acid occasions no precipi- 

 tate in solutions of salts of lime, barytes, or strontian. If hy- 

 drate of lime however is heated in a solution of pyromeconic 

 acid it dissolves, and when the liquor begins to cool the lime- 

 salt is deposited in small hard crystals, the form of which I was 

 unable to determine. 



As Liebig has observed, pyromeconic and pyromucic acids 

 are isomeric bodies; their composition in 100 parts and their 



K2 



