8 ANIMAL ACIDS DESTITUTE OF AZOTE. 



lead, silver, or mercury, nor chloride of calcium. It did not at- 

 tack silver, but dissolved its oxide. It did not dissolve red oxide 

 of mercury, but when digested with it, the mercury was reduced 

 to the metallic state. It did not attack copper, but dissolved its 

 oxide, and formed with it beautiful green crystals. It dissolved 

 iron filings, and yielded small crystals. This, he says, is worthy 

 of remark, because the solution of iron in distilled vinegar does 

 not crystallize. It did not attack lead, but readily dissolved red 

 lead, and formed beautiful crystals similar to those of acetate of 

 lead. It dissolved zinc, and yielded crystals quite different from 

 those of acetate of zinc. It scarcely acted on bismuth or anti- 

 mony or their oxides. It dissolved carbonate of lime with rapi- 

 dity, and formed with it a crystalline mass.* 



In 1781, Arvidson confirmed the observations of Margraaf, 

 and gave ample details respecting the preparation and concentra- 

 tion of this acid.f In 1782, Bucholz showed how it might be 

 obtained in a very concentrated state by forming dry formate of 

 potash, mixing the dry salt with the requisite quantity of sulphu- 

 ric acid and distilling. He formed also a small quantity of for- 

 mic ether.J In 1784, Hermbstadt published an elaborate paper 

 on the preparation of this acid, but did not add much to what 

 was already known. Richter followed in 1793, and proceeded 

 nearly as Bucholz had done.|| Deyeux started the notion that 

 formic was identical with acetic acid, and this was followed up by 

 a set of experiments by Fourcroy and Vauquelin, from which they 

 concluded that it was a mixture of acetic and malic acids. 1F This 

 opinion was called in question by Suerzen, who demonstrated that 

 pure formic acid contains no malic acid, and that its properties 

 were different from those of acetic acid.** This indeed had been 

 already proved by Margraaf; but the French chemists had paid 

 no attention to his experiments. Gehlen resumed the subject in 

 1812, and showed, in the most convincing manner, that formic 

 and acetic acids possess different characters, f f 



Dobereiner discovered a method of preparing formic acid ar- 

 tificially by mixing tartaric acid and binoxide of manganese in a 



* Opuscules Chymiques de M. Margraaf, i. 301. 



t Wieglib's Geschichte, ii. 242. \ Ibid, ii. 269. 



Crell's Annalen, 1784, ii. 209. 



|| Ueber die neueren Gegenstande der Chemie, vi. 135. 



J Phil. Mag. xv. 118. ** Gehlen's Jour. iv. 3. 



j-f Schweigger's Jour. iv. 1. 



