350 Dr. Gladstone on the Compounds of the 



pentabromide; but the final result is a liquid, which, upon 

 the application of heat, evolves bromine, and apparently leaves 

 the original substance behind unaltered. Chlorine displaces 

 the bromine in this compound, red vapours being immediately 

 evolved when it is treated with that gas. 



The analysis of this substance was effected by decomposing 

 it in water, and precipitating the hydrobromic and phos- 

 phoric acids, thus produced, in the usual manner. The re- 

 sults, as given below, fully confirmed the expectation that this 

 new liquid was the oxybromide of phosphorus, having the 

 composition P Br3 O^. 



0*6245 grm. of substance yielded 1*227 grm. of bromide of 

 silver, and 0*1514' grm. of phosphoric acid. 



O'Sll grm. of another preparation yielded 1*605 grm. of 

 bromide of silver. 



Or, calculated to 100 parts, — 



By calculation 

 By experiment. from P Bi-g O2. 



Phosphorus . . 10*77 ... 11*29 



Bromine . . . 82-50 83*11 83*06 



Oxygen ... 5'65 



The production of this oxybromide of phosphorus will be 

 expressed by the equation — 



PBr5 + 2HO=PBr3 02 + 2HBr. 



I have not succeeded in accurately determining the boiling- 

 point of the liquid under consideration. It appears to vary 

 between 1 70° C., and perhaps 30 degrees higher. Kopp finds 

 that the substitution of three atoms of chlorine by three atoms 

 of bromine in a compound, causes an elevation in its boiling- 

 point of 96° C. Thus, the terchloride of phosphorus boils at 

 78" C. ; the terbromide at 175°C. (Pierre), or 174° C, accord- 

 ing to my own observations. Now, as oxychloride of phos- 

 phorus boils at 110° C, this would give as the boiling-point 

 of oxybromide of phosphorus 206° C. ; but experiment cer- 

 tainly does not indicate it as so high. 



I may liere remark that, in the decomposition of this oxy- 

 bromide by water, there is usually formed a small quantity of 

 a brown resinous-looking matter, not acted upon by water, 

 nor soluble either in potash or nitric acid. It has a very 

 characteristic odour. I have never obtained it in sufficient 

 quantity for thorough examination. This readily accounts 

 for the slight loss in the first analysis recorded above. 



Sulpho-bromine Compound. — On passing a stream of hydro- 

 sulphuric acid over pentabromide of phosphorus, combination 

 instantly ensued ; the yellow crystals gave place to a colour- 



