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XXXXI. On Valency, Validity, and Residual Affinity. By 

 J. F. Heyes, M.A., F.C.S., F.R.G.S., of Magdalen College, 

 Oxford* 



THE timely paper by Professor Armstrong, entitled "A 

 Note on Valency, especially as defined by Helmholtz,"f 

 induces me to publish my paper on the tetravalency of 

 oxygen, and to offer some remarks on his paper in the hope 

 that both, so happily coincident and containing independent 

 views and suggestions, will do something to bring forward 

 the consideration of the problems of "Valency which are so 

 essentially characteristic of the present state of Chemical 

 Philosophy. Raw material abounds. It is now surely more 

 essential for chemists to study the inner mechanism, so to 

 speak, of the chemical molecule both in the interrelationships 

 of the parts and the forces concerned than to discover, say, 

 more oxides of manganese when we have already too many. 

 Especially would I venture to direct attention to the paradox 

 which now confronts us in the contrast existing, on the one 

 hand, between so many of the complex organic molecules 

 whose "constitution" we know, or at any rate whose inter- 

 atomic relationships are regular and certain, even to a degree 

 of prediction within remarkable limits, and, on the other, 

 between so many simple inorganic molecules. Why, in fact, 

 should " the constitution " of complex C^H^O*. or CpH g O r N s 

 be known, and simple N z O y remain a puzzle, which tends to 

 make many chemists write the old unitary formula in despair 

 and betake themselves to the seductive studies of molecular 

 physics ? 



In my previous paper % some probable causes of confusion 

 have been discussed which have led to the different views 

 held on valency, but the problem is one for the immediate 

 future. Prof. Armstrong draws our attention to the electric- 

 charge theory of valency — using that term, it is presumed, 

 in the sense of a property of the atom which used to be called 

 atomicity. My paper suggested that valency was primarily 

 a number or numbers, the measure of something whose real 

 character and denomination science is still seeking, but never- 

 theless a something towards whose perception electrical, 

 thermal, and atomic mass ratio constants are rapidly converg- 

 ing. The number and the thing itself should not be con- 

 founded. But our fundamental standpoint in valency is that 



* Communicated by the Author. 



t Phil. Mag. pp. 21-30 of the present volume. 



% Phil. Mag. pp. 221-237 of the present volume. 



