Remarks on Formic Acid. 147 
the integrity of the sulphuric acid ; but, in another respect, namely, 
the abundant deposit of carbon, previous to the escape of the formic 
acid, the action more resembles what occurs when alcohol changes 
at once into carbon and olefiant gas. ‘The resemblance is still closer, 
if, as I suppose to be the case, the agency of the sulphuric acid con- 
sists in removing water, or its elements. from the organic substances 
which yield the formic acid when under its influence. Ihave men- 
tioned that the phosphoric acid may be substituted for the sulphuric. 
In the experiment to determine this, the absence of the latter acid 
was accurately proved by muriate of baryta; starch was employed, 
and the phosphoric acid had the consistency of syrup. But although 
important for the investigation, as a fact, the substitution really cannot, 
in practice, be made with advantage, because the phosphoric acid 
has not the same degree of affinity for water, and before the essen- 
tial action occurs, (well indicated by the separation of carbon,) the 
organic matter becomes decomposed, more or less, from simple ex- 
posure to heat, which thus imparts to the formic acid an unpleasant 
empyreumatic taste. ‘I'he same remark applies to the chloride of tin. 
There is little doubt, therefore, that, under the influence of strong 
sulphuric acid, gum, sugar, starch, lignine, &c. bear the same gene- 
ral relatio nto formic acid, and the latter to oxide of carbon, that alco- 
hol does to Aydric ether, and the latter to olefiant gas or etherine. 
Thus, 
1 Alcohol—furnishes hydric ether. 
Sulphuric acid, Water from | Sug ea ret. * sha acid. 
by subtracting , ther, “  olefiant gas. 
: & (Water from S Form: rmic acid,“ — oxide of carbon. 
By a comparison of combining proportions, it will be seen that this 
explanation enables us to dispose of all the elements except two of 
drog' 
ee by adopting (C-+O+H) as the formula for one atom of 
sugar ; and, supposing four atoms to be the smallest amount involved 
in the process, we will have (4C+4O0+4H), from which subtract 
H, or one atom of water, (removed by the sulphuric acid,) and we 
shall have 4 C+-30+3 H, which is equivalent to one atom of for- 
mic acid (2 C-+3 0 +H) together with 2 carbon, precipitated, and 
2 hydrogen, unaccounted for. Again; assuming (6C+5 O+5 H) 
as s the formula for one atom of starch, and subtracting 2 H, or two 
atoms of water, removed by the sulphuric acid, the remainder will 
be equivalent to one atom of formic acid, (2C+30+H) together 
