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XXXIV. Contributions to the History of the Phosphorus Chlo- 

 rides. By T. E. Thorpe, Ph.D., F.R.S.E.* 



I. On the Reduction of Phosphor yl Trichloride* 



rN his first memoir on Vanadium, Dr. Roscoe described a 

 series of oxychlorides obtained from vanadyl trichloride by 

 the action of reducing-agents. When the vapour of vanadyl tri- 

 chloride is passed together with hydrogen through a heated tube, 

 a bright grass-green crystalline sublimate of vanadyl bichloride, 

 VO CI 2 , is produced in the anterior portion of the tube ; after- 

 wards a layer of vanadyl monochloride, VO CI, is deposited as an 

 exceedingly light, nocculent, brown powder ; whilst at the ex- 

 treme end of the tube beautiful bronze-coloured plates of the 

 divanadyl monochloride, V 2 O 2 CI, are formed, which have the 

 appearance of mosaic gold. In this memoir Dr. Roscoe clearly 

 pointed out the intimate analogy which exists between the com- 

 pounds of vanadium and those of phosphorus, arsenic, antimony, 

 and nitrogen ; and in his subsequent researches on this subject, 

 he has so far elaborated this view of its chemical relationship, 

 that there is no longer room to doubt that vanadium is virtually 

 a member of the trivalent group of elements. 



It must be confessed^ however, that the triatomic nature of 

 vanadium is not very apparent in the oxychlorides derived from 

 the vanadyl trichloride if the simplest formulas derived from their 

 analysis are retained ; but if these formulae be doubled, the diffi- 

 culty at once vanishes. The supposition that these oxychlorides 

 possess a greater molecular weight than the vanadyl trichloride, 

 may derive some support from the fact of the change of physical 

 state whkm accompanies their formation, the lower oxychlorides 

 being all solid. Beyond this I am not aware that any fact is 

 known to establish such an assumption, unless it be the coin- 

 cidence between the atomic volume of the vanadyl trichloride 

 and that of the vanadyl dichloride with the formula doubled. 





Specific 



Atomic 



Atomic 





gravity. 



weight. 



volume 



VOCF . 



. 1-83 



173-8 



95-0 



V 2 O 2 CI 4 . 



. 2-88 



276-6 



96-0 



According to this view, the formulas of these oxychlorides and 

 their relation to the vanadyl trichloride would be graphically 

 represented thus : — 



* Communicated by the Author, having been read at the Meeting of the 

 British Association at Edinburgh, September 1871. 



Phil Mag. S. 4. Vol. 42. No. 280. Oct. 1871 X 



