352 Dr. Gladstone on the Compounds of the 



to destroy the brown salt produced at the same time, estima- 

 ting the sulphuric acid thus formed in the usual manner, and 

 adding the amount of sulphur it contained to that left undis- 

 solved in the aqueous solution. 



I. 0*200 grm. of the liquid yielded 0*075 grm. of sulphate 

 of baryta, and 00702 grm. of phosphoric acid. 



II. 0'373 grm. yielded 0*07255 grm. of bromide of silver, 

 0*0125 grm. of sulphur, and 0'04-5 grm. of sulphate of baryta. 



III. 0*444'5 grm. yielded 0*173 grm. of sulphate of baryta, 

 and 01 36 grm. of phosphoric acid. 



IV. 0*2965 grm. yielded 0*124' grm. of sulphate of baryta, 

 and 0*0848 grm. of phosphoric acid. 



Or, reckoned to 100 parts, — 



I. II. III. IV. 



Phosphorus . . 15'6 ... 13*6 12*8 



Bromine 81 '6 



Sulphur ... 5*2 5*0 5*4 5*7 



This does not accord well with any simple formula. If we 

 suppose it to be a chemical combination of three atoms of ter- 

 bromide with one atom of tersulphide of phosphorus, i. e. a 

 sulpho-phosphite of the bromide of phosphorus, we obtain 

 numbers which are similar. 



Calculated from SPBrs + PS.,- 



Phosphorus 14*5 



Bromine 80*1 



Sulphur 5*4 



1000 



It is possibly, however, amixtureof two distinct substances 

 having nearly the same boiling-point. 



It does not appear that similar compounds belonging to the 

 iodine series exist. Pentiodide of phosphorus is rapidly de- 

 composed by the moisture of the atmosphere, but it did not 

 furnish an oxy iodide. Hydrosulphuric acid has no action 

 on the pentiodide of phosphorus, either at the ordinary tem- 

 perature, or when fused by the heat of a water-bath. ;jii 



It is remarkable to observe the increased stability which 

 these two atoms of oxygen, or sulphur, give to the compound 

 of phosphorus with three atoms of the halogen. Whereas 

 hydrosulphuric acid is capable of completely decomposing 

 both the terchloride and terbroniide of phosphorus, it is in- 

 capable of removing the three atoms of chlorine from the sul- 

 phochloride of phosphorus, and also the remaining bromine 

 from the compound of bromine, sulphur, and phosphorus just 

 described. Again, whilst metals immersed in terchloride of 

 phosphorus, or terbromide, are attacked by them, they remain 



