394 PRINCIPLES OF CHEMISTRY 



belongs to the type PtX 2 , then Gros's salt belongs to the type PtX 4 ), is 

 soluble in water, and the elements of nitric acid, but not the chlorine,, 

 contained in it are capable of easily submitting themselves to double 

 saline decomposition. Thus silver nitrate does not enter into double 

 decomposition with the chlorine of Gros's salt. Most instructive was 

 the circumstance that Gros, by acting on his salt with hydrochloric 

 acid, succeeded in substituting the residue of nitric acid in it by 

 chlorine, and the chlorine thus introduced, easily reacted with silver 

 nitrate. Thus it appeared that Gros's salt contained two varieties of 

 chlorine one which reacts readily, and the other which reacts with 

 difficulty. The composition of Gros's first salt is PtCl 2 (NH 3 ) 4 (N0 3 ) 2 ; 

 it may be converted into PtCl2(NH a ) 4 (S0 4 ), and in general into 

 PtCl 2 (NH 3 ) 4 X 2 .i* 



The salt of Magnus when boiled with a solution of ammonia gives 

 the salt (of Reiset's first base) PtCl 2 (NH 3 ) 4 , and this, when treated 

 with bromine, forms the salt PtCl 2 Br 2 (NH 3 ) 4 , which has the same 

 composition and reactions as Gros's salt. To Reiset's salts there 

 corresponds a soluble, colourless, crystalline hydroxide, Pt(OH) 2 (ISrH 3 ) 4 , 

 having the properties of a powerful and very energetic alkali ; it 

 attracts carbonic anhydride from the atmosphere, precipitates metallic 

 salts like potash, saturates active acids, even sulphuric, forming 

 colourless (with nitric, carbonic, and hydrochloric acids), or yellow 

 (with sulphuric acid), salts of the type PtX 2 (NH 3 ) 4 .! 4 The com- 



13 Subsequently, a whole series of such compounds was obtained with various 

 elements in the place of the (non-reacting) chlorine, and nevertheless they, like the 

 chlorine, reacted with difficulty, whilst the second portion of the X's introduced into 

 such salts easily underwent reaction. This -formed the most important reason for the 

 interest which the study of the composition and structure of the platino-ammonium 

 salts subsequently presented to many chemists, such as Keiset, Blomstrand, Peyrone, 

 Raeffski, Gerhardt, Buckton, Cleve, Thomsen, Jorgensen, Kournakoff, Verner, and 

 others. The salts PtX^NHs, discovered by Gerhardt, also exhibited several different 

 properties in the two pairs of X's. In the remaining platino-ammonium salts all the 

 X's appear to react alike. 



The quality of the X's, retainable in the platino-ammonium salts, maybe considerably 

 modified, and they may frequently be wholly or partially replaced by hydroxyl. For 

 example, the action of ammonia on the nitrate .of Gerhardt's base, Pt(NO 5 ) 4 ,2NH3, in a 

 boiling solution t gradually produces a yellow crystalline precipitate which is nothing 

 else than a basic hydrate or alkali, Pt(OH) 4 ,2NH 3 . It is sparingly soluble in water, but 

 gives directly soluble salts PtX 4 ,2NH 3 with acids. The stability of this hydroxide is 

 such that potash does not expel ammonia from it, even on boiling, and it does not change 

 below 130. Similar properties are shown by the hydroxide Pt(OH) 2 ,2NH 3 and the 

 oxide PtO,2NH 3 of Eeiset's second base. But the hydroxides of the compounds con- 

 taining 4NH 3 are particularly remarkable. The presence of ammonia renders them 

 soluble and energetic. The brevity of this work does not permit us, however, to 

 mention many interesting particulars in connection with this subject. 



14 Hydroxides are known corresponding with Gros's salts, which contain one hydroxyl 

 group in the place of that chlorine or haloid which in Gros's salts reacts with difficulty, 



