FORMIATES. 831 



Formiates of suboxide and oxide of mercury. Red oxide of 

 mercury well pounded dissolves in formic acid, at the ordinary 

 temperature and forms a solid crystalline mass on evaporating 

 in dry air, which is the formiate of that oxide. On applying 

 the slightest heat to this salt either dry or in solution, effer- 

 vescence occurs from the escape of carbonic acid, and formiate 

 of suboxide of mercury is produced. The latter salt is de- 

 posited from a solution so decomposed, in a crystalline very 

 brilliant micaceous mass, which is composed of small plates of 

 4 or 6 sides, of a silky or silvery lustre. By a higher tempe- 

 rature formiate of the suboxide is decomposed whether dry or 

 in solution, with a slight explosion, metallic mercury being 

 liberated with formic and carbonic acids. The decomposition 

 of this salt is thus represented by Liebig : 2 atoms of formiate 

 of suboxide of mercury are resolved by heat into : 



2 atoms of carbonic acid. C 2 O 4 



1 atom of hydrate of formic acid. C 2 H 2 O 4 



4 atoms of metal Hg 4 



C 4 H 2 8 Hg 4 



Formiate of silver is also a salt of sparing solubility. It is 

 obtained by the double decomposition of nitrate of silver with 

 an alkaline formiate, in small leaflets of brilliant whiteness ; it 

 is decomposed by heat and resolved into the metal formic and 

 carbonic acids. 



Artificial oil of ants, C 5 H 2 O 2 (Stenhouse). This name was 

 applied by Doebereiner to the oil which appears in the prepa- 

 ration of formic acid. It was obtained by Dr. Stenhouse in 

 larger quantity than it is produced in the ordinary process, by 

 distilling together equal weights of oatmeal or sawdust and 

 sulphuric acid diluted with its own bulk of water. In the 

 process for formic acid the peroxide of manganese cannot be 

 omitted without greatly reducing the product, but here it is 

 entirely left out. When oil of ants is purified the taste 

 and smell are very pungent and aromatic, resembling 

 oil of Cassia. It catches fire very readily and burns with 

 a strong yellow flame. Its density is 1.1006 at 80.6, (27 

 centig.); its boiling point 334.4 (168 centig.) It is pretty 



