Action of Water on Sulpkurets and haloid Salts. 287 



In a second paper H. Rose takes into consideration the 

 long-disputed point, whether the haloid salts and sulphurets 

 decompose water when dissolved. Judging from analogy 

 and the example of the sulphuret of barium, one would sup- 

 pose that sulphuret of potassium would be decomposed with 

 water into hydrosulphuret and caustic potassa ; the solution 

 of this sulphuret turns red litmus paper blue ; and by its solu- 

 tion in water heat is evolved, and we do not know that sul- 

 phuret of potassium combines with water of crystallization. 

 Rose concludes that the higher sulphurets are not decom- 

 posed by water. The compounds of fluorine are so similar 

 to those of sulphur that we might almost be justified in placing 

 fluorine in a class with sulphur and not with chlorine ; it is 

 possible that on dissolving fluoride of potassium in water, 

 potassa and hydrofluoride are formed. Rose could not ob- 

 tain them separate, but, as is well known, the solution reacts 

 alkaline and also attacks glass. The fluoride of ammonium 

 gives ammonia and hydrofluoride. 



Chlorides of potassium, sodium and ammonium produce 

 a considerable degree of cold when dissolved in water, and 

 hence we may conclude, that on the solution of these salts 

 water is not decomposed. Chloride of calcium evolves heat 

 when dissolved, and Thenard and Gay-Lussac adduced this 

 to prove the decomposition of water, but it is simply a com- 

 bination of the salt with water of crystallization. Chloride of 

 sodium produces less cold than chloride of ammonium, but 

 we know that under certain circumstances the former can 

 combine with four atoms of water. The same is the case with 

 several oxysalts. 



Rose has found that chlorides of antimony and bismuth 

 evolve heat when dissolved, and supposes that they decompose 

 water. As a general approximate rule we may say, that all 

 compounds of bromine, chlorine, iodine, cyanogen and sul- 

 phocyanogen with metals which are equivalent to the basic 

 oxides, dissolve in water without decomposition, while those 

 that represent the acid oxides decompose water. Fluoride of 

 potassium evolves heat, but it combines with water ; the hy- 

 drated salt may be obtained by gentle evaporation, or by 

 adding alcohol to a solution of the fluoride ; it contains four 

 atoms of water. — (Pogg. Ann., vol. lv. pp. 534, 557.) 



It is impossible to give any but an imperfect report of this 

 most excellent paper in these notices without exceeding our 

 limits ; we must most earnestly recommend the perusal of the 

 original to all chemists. 



