Halogens with Phdsphoi'iisP '^ 353 



unaltered in oxychloride, or oxybromide of phosphorus, or the 

 sulpho-bromine compound. Even potassium, which instantly 

 inflames with violence when brought into contact with ter- 

 chloride of phosphorus, will remain quite unaffected in the 

 oxychloride, and combination is not determined even by boil- 

 ing the liquid. It is true, the less easily oxidized metals, such 

 as silver or platinum, are not attacked by terchloride of phos- 

 phorus at any temperature ; but even platinum is acted upon 

 by the pentachloride with the assistance of heat, the com- 

 pound being entirely decomposed. And lastly, whereas the 

 penta-compounds of the halogens with phosphorus may be 

 reduced by means of additional phosphorus, no such reduction 

 of the oxychloride takes place. This substance is also un- 

 affected by iodine, bromine, or chlorine. 



There appears no reason why a compound of phosphorus 

 might not be formed, in which two of the halogens should be 

 associated ; but all my attempts to procure such a body have 

 proved unavailing. Many of the experiments given above 

 were undertaken with that view. It occurred to me also, that 

 since chlorine decomposes both the pentabromide and iodide 

 of phosphorus, hydrochloric acid might possibly effect a par- 

 tial double decomposition ; but I found it had no action upon 

 either. If chloride of mercury and pentiodide of phosphorus 

 be heated together, double decomposition does ensue ; but it 

 extends to the three atoms more intimately connected with 

 the phosphorus, and the two additional atoms of iodine are 

 set free : thus — 



Pl5+3HgCl=PCl3 + 3HgI + 2l. 



Since a halogen, bromine for instance, combines directly 

 with the ter-compound of the same halogen with phosphorus, 

 it appeared not improbable that it might combine readily with 

 another ter-compound. But, when bromine is poured upon 

 the terchloride of phosphorus, it merely sinks to the bottom, 

 and the two liquids cannot be made to mix. If, however, a 

 little iodine be added, a junction is instantly effected, attended 

 with great evolution of heat : when the temperature falls, a 

 red crystalline mass separates, resembling pentabromide of 

 phosphorus when prepared with excess of bromine. In order 

 to prove whether it was really this substance, or some new 

 compound, it was necessary to separate it, if possible, from 

 the accompanying liquid. This could not be effected by di- 

 stillation, and the action of solvents was destructive : purely 

 mechanical means therefore had to be resorted to. A com- 

 pound of bromine and iodine was prepared, and terchloride of 

 phosphorus was allowed to fall into it, drop by drop, as long 



Fhih Mag. S. 3. Vol. 35. No. 237. Nov. 1849. 2 A 



