230 Intelligence and Miscellaneous Articles. 



and dissolve readily in water and alcohol. This acid may be sub- 

 jected to a high temperature without being decomposed ; it does not 

 fuse, but is eventually converted into another acid, which is volati- 

 lized, and a coaly residuum. No empyreumatic oil is formed, nor 

 does it even give any smell of burning. Neither sulphuric nor ni- 

 tric acid acts upon this acid. The substance which Vauquelin sup- 

 posed to be pure acid, was supermellitate of potash. — Hensman's 

 Repertoire de Ckimie, Feb. 1828. 



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ACTION OF ACIDS ON PALLADIUM. BY M. FISCHER OF BRESLAU. 



It is well known that palladium is dissolved by cold nitric acid, 

 without the evolution of either nitrous gas or subnitrous acid. This 

 is also the case with mercury, which dissolves in cold colourless 

 concentrated nitric acid. Cold sulphuric acid does not act upon 

 palladium ; with the assistance of heat, the acid dissolves it with the 

 evolution of sulphurous acid : the solution is of a reddish yellow, 

 and when it is saturated, it deposits a red powder on cooling ; this 

 powder is the neutral sulphate ; it is readily soluble in water, to 

 which it imparts a yellow colour. On the undissolved palladium 

 there remains another powder, which is of a deeper colour ; this is 

 slightly soluble in water, and is the subsulphate. Cold muriatic 

 acid dissolves palladium, and without the evolution of hydrogen. 

 There is no doubt but that the oxidation of the metal is effected by 

 the oxygen of the air ; it does not occur with hot muriatic acid, 

 which is sufficient to prove, that it cannot be derived from any other 

 cause : the vapour which the heat raises preserves the fluid from 

 the contact of the air, and prevents the metal from being oxidized. 

 It is not quite impossible that the solution of the metal in the acid 

 may be effected by the double affinity of the chlorine for the metal, 

 and the hydrogen for the oxygen of the air. More than one extra- 

 ordinary result, which it is not easy to credit, is effected by this 

 double action ; and among others the oxidation of iron by water, the 

 bleaching of linen on meadows, and the dehydrogenation of water 

 by the leaves of plants in the sunshine, are similar phenomena. I 

 had previously observed the solubility of silver in the same acid, 

 owing to a similar cause : the solution of both these metals, neces- 

 sarily occurs but slowly; it is however sufficiently rapid to be render- 

 ed apparent by reagents within twenty-four hours. With respect to 

 the solution of silver, it is sufficient to add water to it to precipitate 

 the luna cornea. Muriatic acid therefore dissolves metals which 

 cannot separate the chlorine, and which cannot therefore be the 

 medium through which the decomposition of water is effected. Mu- 

 riatic acid, as I have satisfied myself by experiment, dissolves in 

 the same manner, and at common temperatures, almost all other 

 metals. Platinum itself saturates aqua regia, upon which it acts in 

 the contact of the air when cold, but the operation goes on very 

 slowly. I ought to mention that in this last experiment I employ 

 a very weak acid. 



Phosphoric acid, assisted by long boiling, oxidizes and dissolves 

 palladium, but on cooling, the phosphorous acid which is formed, 



decomposes 



