150 METALS AND THEIR COMBINATIONS. 



The action of nitric acid is similar to that described above 

 under ferric chloride. The hydrogen of the sulphuric acid is 

 oxidized, and the liberated radical S0 4 unites with the ferrous 

 sulphate, nitrogen dioxide being liberated. 



Solution of subsulphate of iron, Liquor ferri subsulphatis (MonseVs 

 solution). This is a solution similar to the preceding, but con- 

 tains less sulphuric acid, and is therefore looked upon as a basic 

 ferric sulphate, of the doubtful composition Fe 4 05SO 4 . The 

 color of the tersulphate of iron solution is reddish-brown ; that 

 of Monsel's solution is ruby-red. 



Ferric nitrate, Fe 2 6N0 3 . A 6 per cent, solution of this salt is 

 officinal, under the name solution of nitrate of iron, Liquor ferri 

 nitratis, U. S. P., and is made by dissolving ferric hydrate in 

 nitric acid : 



Fe 2 6HO + 6HNO 3 = 6H 2 O + Fe 2 6NO 3 . 

 It is an amber-colored or reddish, acid liquid. 



Ferrous carbonate, FeC0 3 . Occurs in nature; may be obtained 

 by mixing solutions of ferrous sulphate and sodium carbonate 

 or bicarbonate : 



FeSO 4 + Na 2 C0 3 = Na 2 SO 4 + FeCO 3 



The precipitate is first nearly white, but soon assumes a gray 

 color by oxidation. The saccharated carbonate of iron, U. S. P., 

 is made by mixing the washed precipitate with sugar, and dry- 

 ing. The sugar prevents, to some extent, rapid oxidation. 



Ferric carbonate does not exist, the affinity between the feeble 

 ferric oxide and the weak carbonic acid not being sufficient to 

 unite them chemically. 



Ferrous phosphate, Fe 3 2P0 4 . Obtained as a slate-colored pre- 

 cipitate, when sodium phosphate is added to ferrous sulphate. 

 Like all ferrous salts, it absorbs oxygen from the air, becoming 

 darker in color : 



3FeSO 4 + 2Na 2 HPO 4 = Fe 3 2PO 4 -f 2Na,SO 4 + H 2 SO 4 . 



