[ 351 ] 



LX. Extract of a Letter from M. Gehlen, of Berlin, 

 to M. VoGEL, co7itaifiitig somG Remarks, 1st, Upon the 

 Formic and Pyrolartarous Acids ; 'id, Upon Carburetted 

 Sulphur; 3d, Upon the Klehschiefer or Mcnilite of Menil- 

 Montant *. 



1 CANNOT adopt the opinion of Messrs. Fourcroy and Vau- 

 quelin, that the formic acid is analogous to the acetic acid. 

 When we distil in B. M. the expressed juice of ants, we 

 obtain a white liquid, which cannot contain malic acid. 

 Tliib distilled acid, combined with bases and afterwards dis- 

 enoatred by the sulphuric acid, or by any other method, does 

 nut resemble the acetic acid. Lowitz was not able to cry- 

 stallize it under the most favourable conditions. I'o a spe- 

 cific gravity equal to that of the acetic acid, it requires a 

 much greater quantity of bases for its saturation; it forms 

 with them sa<ls which enjoy particular properties; with, 

 copper, for instance, a blue salt in cubes, which melts in 

 its water of crystallization; with alcohol it forms an ether 

 quite different : lastly, it displaces the acetic acid from all 

 its saline combinations. 



It is ths same case with the pyro-tartarous acid, which 

 Messrs. Fourcroy and Vauquelin also maintain to be acetic 

 acid. The acid liquor obtained from the dry distillation of 

 cream of tartar, exposed to a slow evaporation, leaves abun- 

 dance of brownish crystals as a residue, which cannot be 

 acetic acid, neither are they tartarous acid, as my own ex- 

 pcriiiienls and those of M. Hose have proved. 



M. Lainpadius proved, some years ago, that carburetted 

 sulphur, as he calls it, contained no carbon. He also proved 

 that the combination of hydrogenatcd sulphur is not what 

 it has been hitherto thought. 



M. Klaproth has made a new analysis of the kleb' 

 schiefer of Menil-Montaut (common resinitc quartz, or mc- 

 nilite). Tlic results arc different from those he gave in his 



• From Anitahs de CMmic, toiii. Ix. p. 78, 



Vol. 27. No. lOS. ISlaij I807. Z preceding 



