On the Compounds of the Halogens 'with Phosphorus. 345 



to the manner in which the variable quantities enter them. 

 And if we were to take account of tlie powers and products 

 of the displacements of the second order, a further change 

 would be protluced, and one which might be very sensible. I 

 may ))erhaps give the subject a brief consideration at some 

 future opportunity, if not prevented. 



Gunthwaite Hall, near Barnsley, Yorkshire, 

 October 5, 1849. 



XLIV. On the Compounds of the Halogens ivith Phosphorus. 

 % J. H. Gladstone, Ph.D.* 



r\URING the course of my recent examination of the com- 

 -*-^ pounds of phosphorus and nitrogen, I had occasion to 

 prepare considerable quantities of pentachloride of phosphorus; 

 and some observations which I incidentally made upon that 

 substance, induced me to undertake a fuller investigation into 

 such combinations of phosphorus with the halogens. 



It is well known that if chlorine gas be passed over phos- 

 phorus, they combine energetically, forniing in the first in- 

 stance a limpid liquid, which is a combination of three atoms 

 of chlorine with one of phosphorus. If the proper amounts 

 of bromine and phosphorus be brought into contact, a similar 

 terbromide is the result. If one part of phosphorus and 

 twelve parts of iodine be mixed, a red, easily fusible solid re- 

 sults, which appears to be an analogous compound. And 

 again, if a larger quantity of chlorine, or bromine, or iodine, 

 be employed, crystalline bodies are produced, which are com- 

 binations of five atoms of the halogen with one of phosphorus. 

 The same penta- compounds result when an additional quan- 

 tity of the halogen is added to the substance containing three 

 atoms. I have not succeeded in bringing about similar com- 

 binations between cyanogen and phosphorus: in fact, this 

 element may be distilled unchanged in an atmosphere of 

 cyanogen gas. 



These compounds form a very distinctly-marked class of 

 bodies. They are neither acid nor basic ; and they are re- 

 solved by water into the hydracids of the halogens, that is, 

 hydrochloric, hydrobromic, or hydriodic acid, and phospho- 

 rous, or phosphoric acid, — according to the number of atoms of 

 the element replaced by oxygen. In these respects they differ 

 from the combinations of sulphur with phosphorus, which 

 have acid properties, are not readily decomposed by water, 

 and are in fact strictly analogous to the oxygen compounds, 



* Communicated by the Author. 



