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 defiant 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. I have 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 imparls to the formic acid an unpleasant 

 empyreumatic taste. The 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 cf carbon, that alco- 

 hol does to hydric ether, and the latter to olefant gas or etherine. 

 Thus, 



C t;t7 u c ( Alcohol — furnishes hydric ether. 

 OIL- -J \ yVater ivom < ^ n ., r • -j 



Sulphuric acid, 1 ^ bugar, «yc. " Jormic acid. 



by subtracting ) ^/^^g,. from ^ ^^^^^' • " olefiant gas. 



V ( Formic 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 

 hydrogen. 



Thus, by adopting (C + O + H) as the formula for one atom of 

 sugar ; and, supposing/oMr atoms to be the smallest amount involved 

 in the process, we will have (4 C + 4 O-f 4 H), from which subtract 

 H, or one atom of water, (removed by the sulphuric acid,) and we 

 shall have 4 C + 3 0-{-3 H, which is equivalent to one atom o( for- 

 mic acid (2 C + 3 O +H) together with 2 carbon, precipitated, and 

 2 hydrogen, unaccounted for. Again; assuming (6C-1-5 + 5 H) 

 as 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, (2 C + 3 O + H) together 



