896 PRINCIPLES OF CHEMISTRY 



to them, endows them with a particular chemical interest. Thus 

 Kournakoff (1889) obtained a series of corresponding compounds contain- 



tion of the chlorine (and other haloid simple and complex groups) in Gros's salts acts iu 

 a different manner from the other portion, and why only half of it acts in the usual way. 

 But this also is not an exclusive .case. The chlorine in potassium chlorate or in carbon 

 tetrachloride does not react with the same ease with metals as the chlorine in the salts 

 corresponding with hydrochloric acid. In this case it is united to oxygen and carbon, 

 whilst in the platino-ammonium compounds it is united partly to platinum and partly to 

 the platino-ammonium group. Many chemists, moreover, suppose that a part of the 

 chlorine is united directly to the platinum and the other part to the nitrogen of the 

 ammonia, and thus explain the difference of the reactions ; but chlorine united to 

 platinum reacts as well with a silver salt as the chlorine of ammonium chloride, NH 4 C1, 

 or nitrosyl chloride, NOC1, although there is no doubt that in this case there is a 

 union between the chlorine and nitrogen. Hence it is necessary to explain the absence 

 of a facile reactive capacity in a portion of the chlorine by the conjoint influence 

 of the platinum and ammonia on it, whilst the other portion may be admitted as 

 being under the influence of the platinum only, and therefore as reacting as in other 

 salts. By admitting a certain kind of stable union in the platino-ammonium grouping, 

 it is possible to imagine that the chlorine does not react with its customary facility, 

 because access to a portion of the atoms of chlorine in this complex grouping is difficult, 

 and the chlorine union is not the same as we usually meet in the saline compounds of 

 chlorine. These are the grounds on which we, in refuting the now accepted explanations 

 of the reactions and formation of the platino-compounds, pronounce the following opinion 

 as to their structure. 



In characterising the platino-ainmonmm compounds, it is necessary to bear in mind 

 that compounds which already contain PtX 4 do not combine directly with NH 3 , and that 

 such compounds as PtX 4 ,4NH 3 only proceed from PtX 2 , and therefore it is natural to 

 conclude that those affinities and forces which cause PtX 2 to combine with X 2 also cause 

 it to combine with 2NH 3 . And having the compound PtX 2 ,2NH 3 , and supposing that in 

 subsequently combining with C1 2 it reacts with those affinities which produce the com- 

 pounds of platinic chloride, PtCl 4 , with water, potassium chloride, potassium cyanide, 

 hydrochloric acid, and the like, we explain not only the fact of combination, but also 

 many of the reactions occurring in the transition of one kind of platino-ammonium salts 

 into another. Thus by this means we explain the fact that (1) PtX 2) 2NH 3 combines 

 with 2NH 3 , forming salts of Beiset's first base ; (2) and the fact that this compound 

 (represented as follows for 'distinctness), PtX 2 ,2NH 3 ,2NH 3 , when heated, or even when 

 boiled in solution, again passes into PtX 2) 2NH 3 (which resembles the easy disengage- 

 ment of water of crystallisation, &c.) ; (3) the fact that PtX 2 ,2NH 3 is capable of absorbing, 

 under the action of the same forces, a molecule of chlorine, PtX 2 ,2NH 3 ,Cl 2 , which it 

 then retains with energy, because it is attracted^ not only by the platinum, but also by the 

 hydrogen of the ammonia; (4) the fact that this chlorine held in this compound (of 

 Gerhardt) will have a position unusual in salts, which will explain a certain (although 

 very feebly-marked) difficulty of reaction; (5) the fact that this does not exhaust the 

 faculty of platinum for further combination (we need only recall the compound 

 PtCl 4 ,2HCl,16H 2 O), and that therefore both PtX 2 ,2NH 3 ,Cl. 2 and PtX 2 ,2NH 3 ,2NH 3 are still 

 capable of combination, whence the latter, with chlorine, gives PtX 2 ,2NH 3) 2NH 3 ,Cl 2 , 

 after the type of PtX 4 Y 4 (and perhaps higher) ; (6) the fact that Gros's compounds 

 thus formed are readily re-converted into the salts of Beiset's first base when acted on 

 by reducing agents ; (7) the fact that in Gros's salts, PtX 2) 2NH 5 (NH 3 X) ;2 , the newly- 

 attached chlorine or haloid will react with difficulty with salts of silver, &c., because it is 

 attached both to the platinum and to the ammonia, for both of which it has an attraction ; 

 (8) the fact that the faculty for further combination is not even yet exhausted in the 

 type of Gros's salts, and that we actually have a compound of Gros's chlorine salt with 

 platinous chloride and with platinic chloride; the salt PtS0 4 ,2NH 3 ,2NH 3 ,SO 4 com- 

 bines further also with H 3 ; (9) the fact that such a faculty of combination with new 



