Preparation of Formic Acid. 19 
and adjusting to the tubulure a perforated cork and pipette with 
gum-elastic bag for the gradual introduction of sulphuric acid, 
we slowly inject about 1 cubic inch of the latter upon the mix- 
ture. By regulating the addition of the acid and occasionally 
intermitting the slender stream, the violent reaction which ensues 
is prevented from occasioning any very great intumescence. Du- 
ring this stage of the operation, upwards of 2 cubic inches of a clear 
but feebly acid liquid passes over into the receiver. When the ac- 
tion has in a good measure subsided, we add 5 cubic inches more 
of water, and apply a gentle lamp heat, continuing the addition of 
the acid, by allowing it simply to drop from the pipette, until an- 
other. cubic inch has been introduced. (The liquid which now 
passes over is much stronger in formic acid than in the preceding 
stage, andthe distillation may, without impairing the purity of 
the product, be continued until about 7 cubic inches have been 
received. By urging it much beyond this point sulphurous acid 
will be evolved. 
One hundred grains of the liquid thus obtained is angle of 
saturating about seven grains of dry carbonate of soda. Its purity 
is such as to fit it for immediate use in illustrating the striking 
reactions of formic acid and the formiates. Thus— 
1. On adding a small portion of it to a solution of nitrate of 
silver previously curdled by ammonia, and applying heat, the sil- 
ver is promptly reduced wath, a lively effervescence of carbonic 
acid. 
. 2. With a solution of bichloride of mercury, aided by heat, it 
causes a precipitation of . satan sesaneneresaetie of hydrochlo- 
ric and carbonic acids. 
3, Combined. with soda it Gin a cali salt readily carbonized 
by heat and passing into carbonate. 
4. It is not blackened by sulphuric ; acid; but the soda salt acted 
upon by this acid evolves carbonic oxide with brisk effervescence. 
_5. This salt heated with solution.of nitrate of silver or nitrate 
of mercury, cpr the metal with evolution ‘of carbonic 
acid. 
All ina pane are so prompt fd striking as to evince but 
little contamination of the formic acid with other products. 
‘On comparing this process with that commonly employed, we 
are convinced of its superiority, first, on account of the exemp- 
tion of the product from SO,, and ina great degree from other 
