Halogens mth Phosphorus. 355 



small amount of these crystals; and they were observed to 

 form on the yellow pentabromide of phosphorus, when imper- 

 fectly secured from the action of the atmosphere, but before 

 complete conversion into oxybromide. They are perfectly 

 transparent and colourless, with sharply-defined edges; theyare 

 decomposed by water : by the moderated heat of a spirit- lamp 

 they fuse, and immediately sublime. But this fusion is apt to 

 produce an alteration in them : instead of re-crystallizing on 

 cooling, a permanent liquid is sometimes found, having the 

 characters of oxybromide of phosphorus. The only analysis 

 I obtained was made with a very small quantity. 



0*1125 grm. yielded 0*2255 grm. of bromide of silver, and 

 0*048 of phosphate of magnesia. 



Or, reckoned to 100 parts, — 



Phosphorus 12*0 



Bromine . . . . . . 84*2 



Oxygen, or loss ... 3*8 



1000 

 Is this crystalline body isomeric with liquid oxybromide of 

 phosphorus? or is it some compound containing less oxygen? 

 May it not also possibly account for the variations in the boil- 

 ing-point of the oxybromide? 



We are unacquainted, I believe, with any method by which 

 the iodides of phosphorus can be purified from excess of iodine. 

 Thus they have never been analysed. It is on this account, 

 also, that my researches have not been carried so far with the 

 iodine as with the bromine compounds ; nor can I feel perfect 

 confidence in all the results at which I have arrived in refer- 

 ence to them. 



Thus have we seen the manner in which the halogens 

 combine with phosphorus, forming ter- and penta- com- 

 pounds ; and also some methods by which the compounds 

 containing five atoms of the halogen may be reduced to those 

 containing three. The comparative feebleness of the combi- 

 nation of the two additional atoms has been rendered still more 

 evident by the action of certain elementary bodies, and of 

 the compounds of these elements with hydrogen. Among the 

 products of these reactions are an oxybromide of phosphorus, 

 and a sulphur compound of less simple formula. It has also 

 been remarked how the substitution of oxygen, or sulphur, 

 for two of the elements of halogen in a penta-compound, in- 

 creases the force with which the remaining three are combined. 

 And lastly, the great indisposition of any two halogens to enter 

 together into a phosphorus compound has likewise been ob- 

 served. 



2 A2 



