PREPARATION OF FORMIC ACID. 
291 
2. With a solution of bichloride of mercury, aided by 
heat, it causes a precipitation of calomel and the evolution 
of hydrochloric and carbonic acids. 
3. Combined with soda it forms a white salt readily car- 
bonized 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, precipitates the metal with evolution of 
carbonic acid. 
All these results are so prompt and striking as to evince 
but little contamination of the formic acid with other pro- 
ducts. 
On comparing this process with that commonly employed 
we are convinced of its superiority, first, on account of the 
exemption of the product from S0 2 , and in a great degree 
from other impurities ; second, from the much larger amount 
of formic acid obtained by it from an equal weight of the 
oxidising material, sulphuric acid and starch or sugar; and 
third, from the ease with which the action is controlled. 
According to Liebig, (Chem. Org., p. 567,) 10 parts of 
starch, 37 parts of peroxide of manganese, and 30 parts of 
sulphuric acid, yield 3.35 parts of an acid liquid, of which 
100 grains saturate 15 grains of carbonate of soda. This 
corresponds to 7. IS parts of liquid such as we obtain. We 
have thus by the old process 7. IS parts of liquid of equal 
acidity with our product, while the aggregate weight of the 
starch, sulphuric acid, and peroxide of manganese is 7 7. 
Ry* our process we have about 1800 grains of a similar 
acid from 2 too grains of sugar, bichromate of potassa and 
sulphuric acid. In other words, by the new process, ive 
procure about nine times as much formic acid from the 
same weight of the three reacting materials, as by that 
hitherto in use. 
