354) Dr. Gladstone on the Compounds of the 



as the crystals appeared to increase in quantity ; the superna- 

 tant liquid was then poured off, and the crystals were allowed 

 to drain, without free exposure to the atmosphere, and were 

 afterwards transferred to a porous tile also protected from 

 moist air. When they appeared as dry as they were likely to 

 become, they were analysed through decomposition by water, 

 and precipitation of the hydracids by nitrate of silver. 



0'431 grm. of the red crystals yielded 0*910 grm. of bro- 

 mide of silver, and O'llS grm. of chloride of silver. 



This indicates 88*6 per cent, of bromine, and 6*4 per cent, 

 of chlorine. Evidently, therefore, the crystalline body was no 

 combination of both halogens with phosphorus, but merely 

 pentabromide of phosphorus contaminated with a little of some 

 chlorinated compound. The pentabromide requires 92*45 

 per cent, of bromine, and 7*55 per cent, of phosphorus. The 

 reaction that takes place is in all probability very simple, — 



PCl3 + IBr5 = PBr5+ICl3. 



If iodine be added to the terchloride of phosphorus, a red 

 solution is immediately obtained. If this be subjected to a 

 temperature a little below 100° C, a red liquid distils over. 

 Quantitative analysis showed that this was merely a solution 

 of iodine in the terchloride ; that element having passed over, 

 in considerable quantity, with the vapour of the compound, at 

 a temperature far below its own subliming point. In the same 

 manner, if iodine be added to the terbromide of phosphorus, 

 a red liquid is obtained, but without chemical combination. 



Nor does it appear that direct combination will take place 

 between phosphorus and the compounds of the halogens 

 themselves. When the liquid chloride of iodine is added to 

 phosphorus, violent combination ensues ; iodine is liberated ; 

 and, even if a double compound be at all formed (which I 

 doubt), it is destroyed by heat, and resolved into chloride of 

 phosphorus and iodine. Again, if phosphorus be brought 

 into contact with the orange-yellow crystals of terchloride of 

 iodine, a blue colour is instantly developed, as though from 

 the liberation of iodine, and a result is obtained similar to 

 that in the former experiment. 



Before quitting the compounds of bromine and phosphorus, 

 I must mention a crystalline body, which I frequently ob- 

 tained during my investigation of them, but wliich, from not 

 understanding the conditions of its formation, I have never 

 procured in any considerable quantity ; and, in the attempt 

 to purify it, I have almost uniformly destroyed the little I did 

 possess. In distilling terbromide, or oxybromide of phos- 

 phorus, there remained in the retort, on several occasions, a 



