400 Intelligence and Miscellaneous Articles, 



phosphoric acid, or chloride of tin undergo any decomposition, un- 

 less incidentally. 



3. The formic acid may be procured from almost every kind of 

 vegetable matter that is capable of being promptly blackened by 

 contact with strong sulphuric acid. It rarely appears previous to 

 the carbonization*, and only when the sulphuric acid possesses a 

 powerful affinity for water. 



It would appear, from these particulars, that the process for ob- 

 taining formic acid artificially is analogous to those operations for 

 converting cotton, ligneous matter, &c, into gum — gum or starch 

 into sugar, and alcohol into aether or olefiant gas, as far as regards the 

 integrity of the sulphuric acid j but, in another respect, namely, the 

 abundant deposition 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. 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 can- 

 not, in practice, be made with advantage, because the phosphoric 

 acid has not the same degree of affinity for water, and before the 

 essential action occurs, (well indicated by the separation of carbon,) 

 the organic matter becomes decomposed, more or less, from simple 

 exposure to heat, which thus imparts to the formic acid an unplea- 

 sant 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, lignin, &c, bear the same gene- 

 ral relation to formic acid, and the latter to oxide of carbon, that 

 alcohol does to hydric cether, and the latter to olefiant gas or sethe- 

 rine. Thus, 



„.. . ., \ Water from {i lcohol T famh * es ^ dr ¥« l ><f- 

 sulphuric acid, I [ Sugar, <yc. „ formic acid, 



by subtracting ] Wa t er fr om S^Etker, „ olefiant gas. 



L [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 four atoms to be the smallest amount involved 



* When the chloride or sulphate of tin is employed, perfect carbonization 

 does not take place, yet the formic acid is generated readily. There is no 

 doubt, however, that some variety [or combination] of carbon separates at 

 the same time. Sugar, for example, gave a large deposit of a snuff brown 

 colour, and resembling in its properties the ulmin of rotten wood. 



