142 Remarks on Formic Acid. 



will here notice an instance, founded upon my own observation, of a 

 very striking nature. Being lately very much struck with the odor 

 peculiar to the red oak, I applied my li|is closely to the transverse 

 section of some fresh cut logs, and, to my astonishment, sucked up 

 with ease a pure and grateful vinegar, sharp to the taste, and so like 

 the best specimens of the acetic acid that distillation could not have 

 improved its qualities. The tree was full grown and sound, and felled 

 in the month of February, about the 6th, and the wood examined 

 as soon as cut. The acetic acid existed most abundantly in the red 

 portion next to the heart. 



In some of the arts, where pure acetic acid of medium strength 

 is required, (as in making while lead,) it appears to me that the for- 

 mic acid might be substituted ; for, independently of the fact that 

 the latter may be procured pure and concentrated by a single dis- 

 tillation from the same bodies which, indirectly, and only by an 

 expensive process, furnish the acetic acid, — their neutralizing powers, 

 are widely different, and the advantage is greatly in favor of the 

 formic acid. The combining proportions being as follows : acetic 

 acid 50, formic acid 37, it follows that the difference of weight, 

 which amounts to nearly one fourth of the whole acetic acid, would 

 be always available were the formic acid employed for the purposes 

 of saturation. 



This acid, however, can never be brought to the same degree of 

 concentration, because, its elements being in such a ratio as to rep- 

 resent, exactly, 2 atoms oxide of carbon-\-\ atomwater, it readily 

 suffers decomposition when exposed to the influence of sulphuric 

 acid strong enough to remove its constituent water. This, of course, 

 always happens when a formate is decomposed by the commercial 

 sulphuric acid, and nothing can be more characteristic of the pres- 

 ence of formic acid than the brisk effervescence, owing to the escape 

 of pure oxide of carbon, whenever the dry formates are heated with 

 oil of vitriol. There is no odor of formic acid. The acetates, on 

 the contrary, as is well known, furnish the strongest and purest acid 

 when submitted to the same treatment. But although this may be 

 regarded as a defect for some purposes, the formic acid, obtained 

 by decomposing its salts, need never contain more than 20 per cent, 

 of water. 



To the chemist and pharmaceutist, the formic acid is highly inter- 

 esting in consequence of its surprising reducing power ; being, in 

 this respect, superior even to hydrogen. Like the lampic acid, it 

 often promptly revives the noble metals when saline solutions of the 



