692 REPORT — 1892. 



8. Persulphates. By Dr. H. Marshall. 



9. Cobaltic Salts. By Dr. H. Marshall. 



10. Report of the Oommittee on the Bibliography of Spectroscopy. 

 See Reports, p. 192. 



11. Report of the Committee on the Action of Light on the Mydracids of the 

 Halogens in the Presence of Oxygen. — See Reports, p. 192. 



12. Report of the Committee on the Proximate Constituents of the Various 

 Kinds of Coal. — See Reports, p. 264. 



13. Note on Valency or Atomicity. By Wm. Durham, F.R.S.E. 



The author referred to several communications which he had made to the 

 Royal Society of Edinburgh many years ago, and to a paper in the ' Revue des 

 Sciences Gen^rales ' for June last, by Professor Schutzenberger, of the Royal College 

 of France, who puts forth views identical with the author's. 



Although it is quite true that the constitution of matter is atomic, there is no 

 evidence to show that the chemical affinity associated with these atoms acts in 

 units or in an atomic manner, but that on the contrary it acts within certain limits 

 in all proportious, and may be all exhausted in combination, or part of it may be 

 left as a residue too weak to produce a further undoubted chemical compound, but 

 yet of sufficient energy to produce the phenomena of solution. 



Take, for instance, NH3. From this compound it is inferred that nitrogen is a 

 triad, but it is found that this substance can combine with other two monad 

 elements, viz., IICl. To explain this it is said that nitrogen acts sometimes as a 

 pentad, and the resultant compound is represented thus : — 



II 



I 

 II— N— CI 



i{\ 



This must mean that the nitrogen, although already combined with three 

 hydrogen atoms, and presumably possessing less chemical affinity than when free, 

 has yet sufficient energy left, not only to combine with one additional atom of H 

 and one of CI, but also to dissociate the atoms of H and CI combined as IICl. 

 From the known affinities of the substances concerned this appears to the author 

 to be incredible, and Professor Schutzenberger is of the same opinion. Analogous 

 difficulties are found iu double salts, such as the chlorides of platinum and potas- 

 sium, &c. The solution of all these difficulties and many others of a like nature is 

 very simple if it be admitted that chemical affinity is exercised, not in units, but as 

 it were all round in any proportion, according to circumstances. Thus NII4CI may 

 be repi'esented graphically thus, without supposing any residual affinity whatever, 

 although the author believes there is such : — 



