FORMIC ACID. 77 



decomposed with sulphuretted hydrogen: the acid, 

 which is by this means set free, is distilled off and 

 rectified over dried lead or copper formate. Or anhy- 

 drous oxalic acid is dissolved in 70 per cent, formic acid 

 (obtained by carefully heating glycerin with dried 

 oxalic acid) by the aid of gentle heat, the solution 

 allowed to cool, poured off from the oxalic acid that 

 crystallizes out, and rectified. 



Properties. Colorless liquid of a pungent odor, crys- 

 tallizing below ; specific gravity, 1.223 at ; boiling 

 point, 99; fusing point, 4- 1. Acts as a vesicant. 



Decompositions. Concentrated sulphuric acid resolves 

 it into water and carbonic oxide. Heated with mercury 

 or silver oxide, it is converted into water and carbonic 

 acid, the oxides being reduced. 



All formates are soluble in water. 



The salts of the alkalies are deliquescent in the air. 



Ammonium formate, CH0 2 .KH 4 , is decomposed 

 when heated up to 110, forming prussic acid and water. 



Barium formate, (CH0 2 ) 2 Ba, crystallizes in prisms, 

 which are not changed by contact with air. 



Lead formate, (CH0 2 ) 2 Pb. Lustrous, difficultly 

 soluble needles. Copper formate (CH0 2 ) 2 Cu + 4H 2 0. 

 Large, blue, transparent crystals. When heated yields 

 formic acid of 82 per cent. Silver formate CH0 2 Ag. 

 White crystals, which are decomposed when heated, 

 yielding carbonic anhydride, silver, and formic acid. 

 Mercury formate (CH0 2 ) 2 Hg conducts itself in a similar 

 manner ; when heated it is, however, at first converted 

 into the difficultly soluble salt of the suboxide, carbonic 

 anhydride being evolved. 



Methyl formate, HCO.O.CH 3 . By the distillation 

 of sodium formate with methyl sulphate. Colorless 

 liquid of pleasant odor, boiling at 36. 



Ethyl formate, HCO.O.C 2 H 5 . By the distillation 

 of 7 parts dried .sodium formate with a mixture of 10 

 parts sulphuric acid and 6 parts 90 per cent, alcohol. 



7* 



