FORMIATES. 829 



metallic silver or mercury, without leaving the smallest trace 

 of a salt of silver or mercury in the liquor. When the formic 

 acid contains acetic acid, acetate of suboxide of mercury re- 

 mains in solution. Heated with a solution of corrosive sub- 

 limate, formic acid reduces the latter to the condition of calomel, 

 disengaging hydrochloric and carbonic acids ; upon the salts of 

 oxides of mercury and silver, formic acid has the same action as 

 upon the oxides themselves. Metallic peroxides are reduced 

 by it with the aid of heat to the state of protoxides, which 

 combine with formic acid, while carbonic acid gas is dis- 

 engaged. 



Formiates. Formic acid is more powerful than acetic acid ; 

 the salts of both acids are all soluble in water. Formiate of 

 soda is not soluble in alcohol like acetate of soda ; the formiates 

 comport themselves like the free acid, with sulphuric acid; they 

 also when heated in excess with solutions of salts of silver, 

 mercury, platinum or chloride of gold, precipitate these metals, 

 producing a brisk effervescence. The salts of peroxide of iron 

 are coloured deep orange by a formiate. 



Formiate of ammonia, NH 4 O, FoO 3 , crystallizes in square 

 four-sided prisms ; it is very soluble in water. This salt con- 

 tains the elements of 1 atom of hydrocyanic acid and 4 atoms 

 of water : 



NH 4 0, C 2 H0 3 =-H, NC 2 and 4HO. 



It is accordingly converted into these two products when its 

 vapour is carried through a tube at a red heat. 



Formiate of oxide of ethyl, formic ether, EO,FoO 3 . This 

 ether is obtained by distilling 7 parts of dry formiate of soda 

 with a mixture of 10 parts of sulphuric acid and 6 parts of 

 alcohol of 90 per cent. It is a limpid liquid of an aromatic 

 penetrating odour and cooling spicy taste. Its density is 0.912 ; 

 its boiling point 128.12 (53.4 centig.) Formic ether dissolves 

 in 10 parts of water; ammoniacal gas has no action upon it, 

 while solution of ammonia decomposes it like the other alkalies. 

 Formiate of oxide of methyl is lighter than water, and boils 

 between 36 and 38 centigrade ; its odour suggests that of 

 acetic ether. 



