890 PRINCIPLES OF CHEMISTRY 



ammonia. Owing to the influence of the ammonia, the X 2 in th 

 resultant compound will represent the same character as it has in 



2COC1 2 , as PtCla is able to combine with oxychlorides, and forms somewhat stable 

 compounds. 



(D) The faculty of platinous chloride for forming stable compounds with divers sub- 

 stances shows itself in the formation of the compound PtCl 2 ,PCl 3 by the action of phos- 

 phorus pentachloride at 250 on platinum powder (Pd reacts in a similar manner, 

 according to Fink, 1892), The product contains both phosphorus pentachloride and 

 platinum, whilst the presence of PtCLj is shown in the fact that the action of water 

 produces chlorplatino-phosphorous acid, PtCl 2 P(OH) 3 . 



(E) After the. cyanides, the double salts of platinum formed by sulphurous acid are 

 most distinguished for their stability and characteristic properties. This is all the more 

 instructive, as sulphurous acid is only feebly energetic, and, moreover, in these, as m all 

 its compounds, it exhibits a dual reaction. The salts of sulphurous acid, R 2 S0 3) either 

 react as salts of a feeble bibasic acid, where the group SO 3 presents itself as bivalent, 

 and consequently equal to X 2 , or else they react after the manner of salts of a monobasic 

 acid containing the same residue, RSOj^lis occurs in the salts of sulphuric acid. In sul- 

 phurous acid this residue is combined with hydrogen, H(80 3 H), whilst in sulphuric acid 

 it is united with the aqueous residue (hydroxyl), OH(S0 3 H). These two forms of action 

 of the sulphites appear in their reactions with the platinum salts that is to say, salts of 

 both kinds are formed, and they both correspond with the type PtH^. The one 

 eeries of salts contain PtH 2 (S0 3 ) 2 , and their reactions are due to the bivalent residue 

 of sulphurous acid, which replaces X 2 . The others, which have the composition 

 PtR2(S0 3 H) 4 , contain sulphoxyl. The latter salts will evidently react like, acids ; they 

 are formed simultaneously with the salts of the first .kind, and pass into them. These 

 salts are obtained either by directly dissolving platinous oxide in water containing sul- 

 phurous acid, or by passing sulphurous anhydride into a solution of platinous chloride 

 in hydrochloric acid. If a solution of platinous chloride or platinous oxide in sulphurou 

 acid be saturated with sodium carbonate, it forms a white, sparingly soluble precipitate 

 containing PtNa 2 (S0 8 Na) 4 ,7H 2 0. If this precipitate be dissolved in a small quantity ol 

 hydrochloric acid and left to evaporate at the ordinary temperature, it deposits a salt of 

 t*he other type, PtNa!,(S0 3 ) 3 ,H 3 O, in the form of a yellow powder, which is sparingly 

 eoluble in wafer. The potassium salt analogous to the first salt, PtK 2 (S0 3 K) 4 .2H 2 O, is 

 precipitated by passing sulphurous anhydride into a solution of potassium sulphite in 

 which platinous oxide is suspended. A similar salt is known for ammonium, and with 

 hydrochloric acid it gives a salt of the second kind, Pt(NH 4 ) 2 (S0 3 ) 2 ,H 2 0. If ammonio- 

 chloride of platinum be added to an aqueous solution of sulphurous anhydride, it is first 

 deoxidised, and chlorine is evolved, forming a salt of the type PtX 2 ; a double decompo- 

 sition then takes place with the ammonium sulphite, and a salt of the composition 

 Pt(NH4) 3 Cl 8 (80 3 H) is formed (in a desiccator). The acid character of this substance is 

 explained by the fact that it contains the elements SO 3 H sulphoxyl, with the hydrogen 

 not yet displaced by a metal. On saturating a solution of this acid with potassium 

 carbonate it gives orange-coloured crystals of a potassium salt of the composition 

 Pt(NH4) 2 Cl 3 (S0 3 K). Here it is evident that an equivalent of chlorine in PtfNH^C^ is 

 replaced by the univalent residue of sulphurous acid. Among these salts, that of the 

 composition Pt(NH4) 2 Cl a (S0 3 H) 2 ,H 2 is very readily formed, and crystallises in well- 

 formed colourless crystals; it is obtained by dissolving ammonium platinosochloride, 

 Pt(NH4) 2 Cl4, in an aqueous solution of sulphurous acid. The difficulty with which sul- 

 phurous anhydride and platinum are separated from these salts indicates the same basio 

 character in these compounds as is seen in the double cyanides of platinum. In their 

 passage Into a complex salt, the metal platinum and the group S0 3 modify their 

 relations (compared with those of PtX a or S0 3 X 2 ), just as the chlorine in the salts KC1O, 

 KC10, and KC10 4 is modified in its relations as compared with hydrochloric acid or 

 potassium chloride. 



