Dr. Kane on the Compounds of Ammonia. 45 



most beautiful instances of isomorphism, crystallize without that equivalent of 

 water, and the emgirical formul£e 



S03 + Ag-0 + 2NH3 



cro3 + A^o4-2NH3 

 seo3 + Ag-o+2NH3 



assume from the above principles the form 



so, 



-|- NHj.HO + Ag'NHj. 



'3 



cro 



3 



sec. 



Of these I have re-examined only the sulphate, and that without observing any 

 fact new in its history. 



When chloride of silver is dissolved in water of ammonia, rhomboidal tables 

 are produced, white and opaque, consisting of an ammonia-chloride ; they lose 

 ammonia, however, immediately on being removed from the solution, and hence 

 their quantitative analysis became impossible. 



VIII. OF THE AMMONIA-CHLORIDE OF ZINC. 



When water of ammonia is added to a solution of chloride of zinc, the white 

 precipitate of basic chloride which is at first produced, soon redissolves, and a 

 colourless liquor is obtained, from which, by evaporation at a moderate tempera- 

 ture, crystals may be obtained. These crystals, however, according to circum- 

 stances, present very different appearances, and possess quite different properties 

 and composition, and hence the proper methods of obtaining each variety, in a 

 state fit for accurate examination, must be noticed. The plan which I found 

 most successful was to take a strong and hot solution of chloride of zinc in water, 

 to pass into it a stream of gaseous ammonia, until the precipitate was completely 

 redissolved, and filtering very rapidly, in order to separate any traces which might 

 yet remain of turbidity from undissolved material, to allow the whole to cool. A 

 substance, in very minute, but brilliant plates, of a peculiarly soft and talcy feel, 

 and pearly lustre, is deposited, while the liquor cools ; but after it has cooled, 

 then by further evaporation a completely different salt is formed, which crystal- 

 lizes in stellated groups of square prisms of a brilliant vitreous lustre, and hard to 



