Salis ofMeconic and Komenic Acids. 193 



The salt employed in these determinations was made at 

 three different times ; that used for the first and second de- 

 terminations was washed with hot water, the others were 

 washed with cold water. The salt is evidently tribasic with 

 2 atoms water, and its formula is consequently Me + 3PbO + 

 2aq. I have been quite unable to obtain Robiquet's salt: 

 Me + 2PbO + aq. 



When meconate of ammonia is added to a solution of ace- 

 tate of lead, rendered also slightly alkaline by ammonia, still 

 more basic salts are formed. They fall as deep yellow inso- 

 luble precipitates. In the course of three trials I was quite 

 unable to procure them of definite composition. The mean 

 of several determinations of one quantity gave 68-38 per cent, 

 oxide of lead, a second gave 74-76, and a third 71*07 per 

 cent. The first quantity was washed with hot, and the other 

 two with cold water. 



Meconic Acid and the Per salts of Iron. 



When meconic acid is added to a solution of any of the 

 persalts of iron, the liquid, as is well known, immediately as- 

 sumes a blood-red colour ; but even though very concentrated 

 it may be kept for any length of time without its giving any 

 precipitate. With an alcoholic solution of meconic acid the 

 result is precisely similar. 



If, however, a tolerably concentrated aqueous solution of 

 meconic acid is first neutralized with ammonia, and then treated 

 with a slight excess of very neutral persulphate of iron, after 

 standing for a few hours a fine bright crimson precipitate ap- 

 pears in considerable quantity. This powder, which is not at 

 all crystalline, should be collected on a filter and washed with 

 cold water till the liquid which passes off is but slightly co- 

 loured, and ceases to give any indication of containing sul- 

 phuric acid. The red precipitate is not very soluble in cold 

 water or alcohol, but dissolves very readily either in an acid 

 solution or in hot water. When its solution is treated with 

 potash or soda it is instantly rendered colourless, and the smell 

 of ammonia becomes very perceptible. The iron is precipitated 

 in reddish flocks, evidently in the state of peroxide, for when 

 redissolved in muriatic acid, and tested with red prussiate of 

 potash, not the slightest blue tint is perceptible. 



Phil. Mag. S. 3. Vol. 25. No. 165. Sept. 1844. O 



