TRANSACTIONS OF THE SECTIONS. 27 



general bearing, in which Deville has for some time teen engaged, viz. the pheno- 

 mena of dissociation, as he has termed the partial decomposition which com- 

 pound gases experience under the influence of a temperature more or less elevated. 



A very striking result was obtained by the use of an apparatus similar to that 

 employed in the experiments just described, but in which a brass or silvered tube 

 was substituted for the platinum or iron tube. A rapid flow of water was maintained 

 through the metallic tube, so that it was kept quite cool, whilst the outer porcelain 

 tube was gradually raised to an intense heat as before. On transmitting a current 

 of pure and dry carbonic oxide through the porcelain tube, the lower part of the 

 surface of the cold metallic tube became covered with deposited carbon, whilst a 

 portion of the carbonic oxide, by combining with the oxygen previously united with 

 this carbon, became converted into carbonic anhydride. 



Sulphurous anhydride was by similar treatment resolved into sulphur and 

 sulphuric anhydride; and even hydrochloric acid was partially separated into 

 hydrogen and chlorine. These experiments are intimately connected with the 

 attempts made to explain the cause of certain exceptions to Ampere's law, that 

 equal volumes of gases or vapours contain the same number of molecules of each. 

 Chemists now generally assume that the molecule, both of simple and of compound 

 bodies, forms two volumes of vapour, and consequently that the molecular weight 

 of any substance corresponds with the number which represents twice its density 

 when referred to the density of hydrogen, if this be taken as unity. But there are 

 exceptions to this law: pentachloride of phosphorus, hydrochloride of ammonia, 

 hydnodate of phosphuretted hydrogen, and various other bodies, instead of 

 forming two volumes when one molecule of each is converted into vapour, yield 

 four volumes. 



In order to explain these anomalies, Kopp and Cafinizzaro suppose that, at the 

 temperature at which the vapour-densities of these compounds are observed, the 

 bodies are temporarily decomposed, and, instead of forming one homogeneous 

 vapour, are at the time of the observation really composed of a mixture of vapours. 

 In certain cases this explanation is probably the true one; but its general accept- 

 ance has been disputed by Deville himself, though his results on dissociation seem, 

 to cursory observation, to be in its favour ; and it must be admitted that, up to the 

 present time, the arguments and experiments which he has brought forward in 

 opposition to the views of Kopp and Cannizzaro have not been satisfactorily 

 answered. 



No sufficient proof, for example, has yet been adduced that the well-known 

 anomalous cases of nitric oxide, chlorous anhydride, hydrosulphide of ammonium, 

 cyanide of ammonium, and various other salts of ammonium and the volatile bases 

 are due to dissociation of their components. 



This subject is one, however, too intimately connected with the molecular 

 theories at present under discussion to remain long in its actual state. New ex- 

 periments and evidence will no doubt be forthcoming, which will throw further 

 light upon the cause of these outstanding exceptions. 



Notes on Compounds of Copper and Phosphorus. By F. A. Abel, F.R.S. 



Mr. Abel gave an account of experiments instituted by him a few years ago upon 

 the several combinations of phosphorus with copper, and upon the properties of 

 copper containing small proportions (from 0-3 to 4 per cent.) of phosphorus, with 

 special reference to their application to military and other purposes, as substitutes 

 for the copper and tin alloy Known as gam-metal. 



Mr. Abel's experiments confirmed H. Rose's statements with reprard to the for- 

 mation of the phosphides having the composition Cu B P and Cu 3 P, but showed 

 that the diphosphide of copper (Cu 2 P) could not be produced by the action of 

 hydrogen at a high temperature upon the diphosphate, as stated by Rose. The 

 product richest in phosphorus, obtained by this method, approached in composition 

 to the hexaphosphide, but, generally, the proportion of phosphorus found in the 

 products, after separation of the phosphoric acid produced, was between 3 and 

 8 per cent. The diphosphide of copper heated to redness, out of contact with 

 air, or in a current of hydrogen, was moreover found to be reduced to the hexa- 

 phosphide. 



