Chemistry and Physics. 483 



phur vapor being carried over with that of the persulphide. — Bid. 

 Soc. Ch., II, xliv, 169, Sept., 1885. G. f. b. 



5. On the Valence of Phosphorus. — The valence of the ele- 

 ment phosphorus has long been an open question. On the one 

 side the compound PC1 6 has been regarded as proof of its pentad 

 character; while on the other, thispentachloride has been consid- 

 ered a molecular compound consisting of a molecule of the ter- 

 chloride united to a molecule of chlorine, PCI, . Cl 5 . Even the 

 oxychloride POCl 9 , may be written either 0=P=C1 or Cl 2 = 

 P— O — CI to accommodate the former or the latter view. Mi- 

 chaelis and La Coste have now thrown some light upon this 

 question ; and this for the first time from the purely chemical side. 

 In 1882 the former of these chemists, in connection with Gleich- 

 mann, discovered a body of the composition PO(C 6 H B ) s which he 

 called triphenyl-phosphine oxide. It was prepared by warming 

 the hydrate, which itself was obtained either by the action of 

 sodium hydrate upon triphenyl-phosphine dibromide, or by acting 

 with potassium chlorate and hydrogen chloride upon triphenyl- 

 phosphine ; processes analogous to those by which phosphorus 

 oxychloride is formed either from the pentachloride or the tri- 

 chloride. The substance is a solid body, of specific gravity 1-2124 

 at 22'6 , having a vapor density of 9 - 9. The authors have now 

 succeeded in preparing another body having the empirical for- 

 mula (C 6 H 5 ) 3 PO, by the action of phenol upon diphenyl phospho- 

 rous chloride. This therefore must have the constitution (C 6 H 5 ) 2 

 PO (C B H B ). Hence if phosphorus is trivalent and its oxychloride 

 is C1 3 =:P — O — CI, this compound must be identical with tri- 

 phenyl-phosphine oxide above described. But these bodies, whose 

 molecular magnitudes are both expressed by the formula C 18 H 1S 

 PO, are radically different in physical as in chemical properties. 

 Triphenyl-phosphine oxide as already stated, is a solid body fus- 

 ing at 153*5, and completely indifferent to bromine, oxygen, 

 sulphur, selenium, benzyl chloride and methyl iodide; while the 

 isomeric phenoxyl-diphenyl-phosphine is a thick oily liquid, which 

 readily combines not only with the elements above mentioned^ 

 but with the alkyl-halogens to form crystallizable addition pro- 

 ducts ; a property characteristic of the compounds of trivalent 

 phosphorus. The constitution of this phenoxyl-diphenyl-phosphine 

 therefore can be expressed in a formula only by considering it as 

 a derivative of an isomeric phosphorus oxychloride at present 

 unknown, which contains trivalent phosphorus, thus : 



Phenoxyldiphenyl-phosphine Triphenyl-phosphine oxide 



III T 



r (C.HJ.P-O-C.H. (C 6 H 5 ) 3 P=0 



Isophosphorus oxychloride Phosphorus oxychloride 



III T 



Cl 2 P.OCl C1 S P=0 



(unknown.) 



Hence phosphorus and the other elements of that group must be 

 considered quinquivalent, and the compounds into which these 

 elements enter with a less valence, as unsaturated. — Per. Berl. 

 (Jhem Ges., xviii, 2118, Sept., 1885. g. f. b. 



