Tetravalency of Oxygen. 231 



I prefer to take their suboxides as 



Hg=0=Hg, Cu=0=Cu (not | )0). 



k 



< . 



There is no clear evidence of the Hg — Hg association. 



Similarly for Cu 2 Cl 2 and Hg 2 Cl 2 , usually assumed as 

 Cu— CI Cl=Hg Cl=Cu 



| , I should prefer | and | as being more 



Cu— CI Cl=Hg Cl=Cu 



in accordance with the facts of the reactions of these bodies. 

 The cases of the chlorides and double chlorides are very well 

 known. 



(iii.) There are certain suboxides which lurk in our text- 

 books and literature. In addition to Ag 4 IV , perhaps the " blue 

 crust " forming on recently cut potassium is K 4 IV , and Pb 2 

 may be Pb=0=Pb giving PbO, which can, like BaO, take 

 up more oxygen from the air. Indeed the curious actions of 

 heat on PbO and BaO as well as Mn0 2 &c. seem to be due 

 to this conditional tetravalency of oxygen, and not to change 

 of valency of metallic atom or atoms usually assumed. 



(iv.) The peroxides of potassium and sodium are puzzles. As 

 Na 2 2 is not decomposed on heating, it has a legitimate claim 



0— Na 



which H 2 2 has not. Moreover it forms a hydrate 

 -Na 



Na 2 2 . 8H 2 0. Whatever K 2 4 may turn out to be, it is 

 probable that all the atoms are not divalent. The arrange- 

 ment is undoubtedly a comparatively stable one, and w T hen 

 it is interpreted we shall probably see the constitution of, 

 or at least the interrelations of, certain bodies not usually 

 associated with it, e.g. K 2 4 , KC10 4 , H010 4 , C1 2 4 , all 

 strikingly " stable." Perhaps 



K-0=0 K -0==0 



K-0=0 ° r K-0=-0 



may serve to suggest the problem before us. 



(v.) But just as the remarkable way in which so many metallic 

 chlorides combine with other chlorides,, chlorhydric acid, and 

 oxides, is a strong line of evidence for the trivalency of chlorine, 

 so the peculiar actions of water as an active chemical reagent, 

 even when it is not represented in our conventional equations, 

 seem to be strong evidence of the ready way in which the 

 oxygen atom in water can be stimulated, so to speak, to exhibit 

 its tetravalent character. 



We may recall the way in which " aldehyd hydrate 

 K2 



to <t 



