Biographical Memoir of Sir Humphry Davy. 19 



This was iodine^ discovered by M. Curtois, a dealer in salt- 

 petre, well skilled in chemistry, a substance on which M. Gay- 

 Lussac * and Mr Davy made some curious experiments-)*. 



Fluoric acid, to discover the base of which many fruitless at- 

 tempts had likewise been made, was soon arranged in the same 

 class, according to a suggestion of M. Ampere \. At last, Gay- 

 Lussac himself discovered a combination of carbon and azote 

 (cyanogene) which acts like chlore, fluor, and iodine, and which 

 produces acids without the addition of oxygen. Prussian blue is 

 the well known produce of one of two acids and the oxide of iron. 



Henceforth it is an admitted doctrine in chemistry, that aci- 

 dity depends on the mode of combustion, and not on a material 

 principle ; and the name of Mr Davy is attached to this im- 

 portant proposition, not because he was the only individual by 

 whom it was established, but because he was the first to announce 

 it with precision. It is, in fact, this explanation of phenomena, 

 under a clear and general form, which constitutes invention in 

 the eyes of the majority, who are unable to follow in detail the 

 various phases through which a truth is obliged to pass, before 

 it become matured for ordinary minds. 



By these three grand series of investigations, relating to the 

 chemical action of the pile, the metallization of alkalies, and 

 their combination without oxygen, — by the truths of primary 

 importance which resulted from them, — by the multitude of 

 new experiments, new views, and exquisite appreciation of all 

 the phenomena which had concurred in the demonstration of 



• Sur un nouvel acide formd avec la substance decouverte, par M. Cour- 

 tois. Inst. 6th Dec. 1813. Ann. de Chim. torn. Ixxxvii. p. 311. Note sur la 

 combinaison de I'iode avec Poxygene. Inst. 20. Dec. 1813. Ann. de Chem. 

 Ixxxviii. p. 319. 



Mem. sur I'iode. Inst, ler Aoiit, 1814. Ann, de Chem. torn. xci. p. 1. 

 Bullet. Phil. 1814, p. 112. 



-j- Some experiments and observations on a new substance which becomes 

 a violet-coloured gas by heat. Roy. Soc. Lond. 20th Jan. 1814. Phil. Trans. 

 voL civ. p. 74. Ann. de Chem. tom. xcii. p. 89. Jmm. de Phys. torn. Ixxix. 

 p. 153. Biblioth. Brit. vol. Ivi. p. 248. 



Further experiments and observations on iodine. Roy. Soc Lend. 16th 

 June 1814. Phil. Trans, vol. civ. p. 487- Biblioth. Brit vol. Ivu. p. 243. 



t Ann. de Chimie et de Physique, tom. ii. p. 20. M^moire sur un Classi- 

 fication naturelle pour les corps simple. Ann. id. tom i. p. 295 and 373. 

 lom. ii. p. 5. et 105. 



b2- 



