228 Mr. J. F. Heyes on the 



would be preferable to accept the high valencies of metals 

 suggested. But this is not necessary; and still less necessary 

 is it to return in despair to unitary formulas. Both extremes 

 seem to involve the idea that the atom of highest valency is a 

 sort of nucleus in the molecule, and enforces an immediate 

 proximity or association of all the other atoms of inferior 

 valency*. Organic chemistry has clearly shown that this is 

 not true. It is thus most improbable that avoiding the 

 controversial dot ( . ) in such ways as 



(NH 4 ) 4 SnF 8 , instead of SnF 4 . 4NH 4 F, 



and similarly, 



K 3 HSnF 8 , Am 2 ZrF 6 , Am 3 ZrF 7 , Na 5 ZrF 13 , Cu 2 ZrF 8 + 12H 2 0, 



should involve changes in the already high valency of tin or 

 zirconium. Similarly, in H 2 PtCl 6 it is not very probable that 

 Pt is octovalent; nor in K 2 BeF 4 that beryllium is hexavalent. 

 The alternative is that the halogens are in some compounds 

 more than monovalent. This view I have taken during the 

 last five years. But we need not, as Wurtz appears to have 

 done, take the higher valency as more than trivalent ; for it 

 is not likely that the halogen atom, any more than the 

 metallic atom, is directly associated with all the others. This 

 hypothesis of the occasional trivalency of the halogens (espe- 

 cially iodine, whose evidence is the strongest f), together 

 with the not infrequent tetravalency of oxygen will, I think, 

 be found to simplify our ground very much and practically 

 reduce alternative valencies to two — an alternative which, in 

 the case of such elements as phosphorus and tin, has been 

 recognized for many years. 



The elements may, indeed, be arranged in two divisions, 

 viz. those whose valency is a single number unchallenged 

 {e.g. K, Na, Ba, Sr, Ca, Mg, Zn, Cd), and those whose 

 valencies are more than one number but probably only 



* To take a metaphor, we are apt to look at the maypole, and the 

 children dancing round it, and to neglect the possible interactions of the 

 children themselves, even granted there is juvenile (chemical) equality 

 among them. 



t E. g. IC1 3 , IAc~ 3 , 



Au 2 I 2 (?)or Au=I, Til, Cu.J, or Cu=I— I=Cu, 

 Cu=Cl— Cl=Cu. 

 Tl— I 

 Aul,(?), Til, or || || KI3.NHJ3.CaI,. 



I— I 



PEtJ or Et 3 P=IEt, 

 PEt 4 I 3 , NEt 4 I, &c. 



