306 Mr. J. F. Heyes on Valency, 



But in the red compound the chlorine is trivalent, or at least 

 tervalid, and the nitrogen quinquivalid, 



C1=NH 3 _ 



\C1=NH 3 



It will also be noticed that both PtCl 2 and PtCl 4 are, as the 

 phrase goes, " unsaturated compounds." This could not well 

 be the case if the valency of the platinum were altered in 

 PtCl 4 ; and they must therefore be due to the tervalidity of 

 the chlorine, rather than the tetravalency, or to the residual 

 affinity of the platinum. Thus, PtCl 2 yields (PtCl 2 P)Cl 3 , 

 PtCl 2 P(OH) 3 , and PtCl 2 2PCl 3 , and PtCl 2 P 2 (OH) 6 . In such 

 cases, apparently, the higher valencies must be attributed to 

 the non-metallic elements. The three compounds, 



PtCl 2 . OC, 



PtCl 2 . 20C, 



PtCl 2 . 30C, 



are well worthy of consideration. It is at least obvious that 

 the supposed dominant valency of the Pt is not concerned, 

 but that the tervalidity of chlorine and the quadrivalidity of 

 oxygen most probably are. And if we remove the so-called 

 but very doubtful " polyad," Pt and examine the following 

 series*, this will be still more apparent: 



NH 3 . C1H, 

 NH 3 . 2C1H, 

 NH 3 . 3C1H. 

 Certainly such a series suggests an analogy to the residual 

 charge of a leyden jar, especially when we bear in mind 

 Maxwell's observation that a dielectric composed of strata of 

 different sorts gives the residual effect, although none of the 

 substances alone do so. 



These examples must suffice to show the meaning which 

 may be provisionally attached to the conception of validity, 

 with the following general results: — 



(1) Very high and shifting valencies for the elements are 

 improbable and unnecessary. 



* Another striking set of triplets has just been discovered by Moissan 

 (French Academy of Sciences, Feb. 20, 1888), 

 KF . FH, 

 KF . 2FH, 

 KF . 3FH. 



Fluorine is indeed clearly tervalid, to say the least ; and its very isolation 

 by Moissan seems due to the combination K — F=FH or K — F == FH. 



