248 Intelligence and Miscellaneous Articles. 



potassium, which are readily separated by treating the mixture with 

 water, which dissolves the chloride of potassium and of calcium, 

 while the magnesia is left ; from the mixture of chloride of potassium 

 and of calcium, the lime is precipitated by carbonate of soda. — 

 Journal de Pharm. July 1839. 



MODE IN WHICH SOME SALTS ACT IN HYDROGEN GAS. BY 

 WOHLER. 



Some researches on the peculiar mode of composition of mellitic 

 acid, have caused me to observe that the salt of silver of this acid, ex- 

 posed to pure hydrogen gas at 202°, very quickly changed from 

 its white colour to black, and was afterwards soluble in water and 

 imparted a deep red colour to it. During this reaction a little water 

 was formed, and it lost oxygen, equal to half the weight of that 

 contained in the oxide. The brown solution of the altered salt was 

 strongly acid, and deposited after some time bright metallic silver, 

 and became colourless ; it then contained merely the common co-* 

 lourless salt dissolved in free acid. 



This circumstance indicated with great probability, that by the 

 action of the hydrogen upon this salt, the silver was reduced to the 

 state of protoxide, a supposition which was completely confirmed 

 by examining into the modes in which other salts of silver exist, 

 and the existence of a protoxide of silver was satisfactorily deter- 

 mined. 



Of some other salts of silver which I carefolly examined with 

 this view, the nitrate was that which evinced the most evident al- 

 teration. When exposed at 212° to a current of dried hydrogen 

 gas, it becomes throughout the mass, and very quickly, of a deep 

 brown colour. The action even begins at common temperatures, 

 as it does with the mellitate. The mass is then a mixture of nitrate 

 of protoxide and free nitric acid. Half of the oxygen of the oxide 

 of silver is disengaged in the state of water, from two atoms of the 

 salt of the deutoxide ; there is formed Ag- O, which remains com- 

 bined with half of the acid, whilst the other half is set free. Water 

 dissolves the free acid, and as soon as the principal part of this is 

 removed, the protosalt begins to dissolve in the pure water with a 

 deep red colour. In the dry state this salt is a powder of a deep 

 brownish black colour. When heated it decomposes with a much 

 weaker detonation than the white deutosalt. It then leaves 76 per 

 cent, of metallic silver, a quantity which ought to remain according 

 to the formula Ag C^ H^ O*. 



If the red solution of the protosalt be boiled, it gradually decom- 

 poses with a slight disengagement of gas ; it becomes opalescent 

 and of a peculiar yellowish green colour ; afterwards it deposits me- 

 tallic silver, and becomes colourless. The brown protosalt dissolves 

 in ammonia also with a %'ery deep yellowish red colour. When 

 heated the solution undergoes a decomposition similar to the pre- 

 ceding. Sometimes the sides of the vessel are covered with a bril- 

 liant metallic coating almost of a golden colour, and which, like 

 very finely divided gold, is transparent and of a fine green colour. 



