Halogens mth Phosphorus. * 351 



less or slightly red liquid, whilst hydrobromic acid was evolved: 

 no free bromine or bromide of sulphur was observed. When 

 the action was complete, the new product was first heated in 

 a water-bath to drive ofiP excess of hydrosulphuric acid, and 

 then distilled at about 200° C. A colourless dense liquid 

 passed over ; but analysis showed that it was not the sulpho- 

 bromide expected. The estimations, Nos. 1 and 2, recorded 

 below, were made from it. Fearing that a decomposition 

 might have taken place in the distillation of this substance, I 

 submitted some carefully prepared pentabromide of phos- 

 phorus to the action of dry hydrosulphuric acid, and examined 

 the resulting liquid itself. It was colourless, or slightly red, 

 of high specific gravity, and fumed in moist air, giving forth 

 a disgusting and deleterious odour. It was slowly decomposed 

 by water, sulphur being deposited, and hydrobromic and 

 phosphorous acids being dissolved : there was also in solution 

 a sulphide of phosphorus, which gave a brown precipitate with 

 a silver salt, but no hydrosulphuric acid. If alkali were added 

 to the water, decomposition took place much more rapidly. 

 It was soluble in aether, insoluble in cold sulphuric acid ; but 

 upon raising the temperature to about the boiling-point of the 

 substance, decomposition ensued, the sulphuric acid became 

 red, hydrobromic acid was evolved, and afterwards bromide 

 of sulphur. Strong nitric acid attacked it violently ; the phos- 

 phorus and sulphur being oxidized, the bromine dissipated. 

 When treated with bromine, it gave momentarily the yellow 

 crystals of pentabromide of phosphorus ; then gas was evolved, 

 and it again became liquid. It boiled at about 200° "C. with- 

 out alteration. The quantitative estimation of its elements 

 gave analysis No. 3, proving its identity with the liquid first 

 analysed. 



As the hydrosulphuric acid employed in these experiments 

 was made li*om sulphide of iron, and was dried by passing 

 through sulphuric acid, I suspected that free hydrogen might 

 possibly have interfered with the reaction, although it does 

 not affect pentabromide of phosphorus itself when alone. The 

 experiment was therefore repeated with hydrosulphuric acid 

 prepared from sulphide of antimony, and dried by means of 

 chloride of calcium. When the resulting colourless liquid was 

 thoroughly saturated with the gas, it was found to be similar 

 to that previously obtained. It afforded analysis No. 4. 



The analyses numbered 1, 3, and 4 were performed by 

 oxidizing the liquid by means of nitric acid. The second ana- 

 lysis was obtained by allowing the liquid to remain under 

 water until entirely decomposed, precipitating the bromine by 

 nitrate of silver, heating the precipitate with nitric acid in order 



