104 On Iodine. [Feb. 



red matter which phosphorus so often furnishes, and which is at 

 present considered an oxide. But 1 have not compared the two 

 bodies, as I had no oxide of phosphorus in ray possession. Very 

 little oxygen seems to be necessary to convert phosphorus into this 

 led matter; and as the phosphorus which I employed, though well 

 wiped, was not quite free from humidity, the formation of this 

 substance during my experiment does not present any difficulty. 

 It is a subject of investigation which deserves to fix the attention of 

 chemists. 



In whatever proportions the ioduret of phosphorus has been 

 made, it exliales, as soon as it is moistened, acid vapours, owing 

 to the hydriodic acid formed by the decomposition of the water. 

 To obtain this gas without any mixture of phosphureted hydrogen, 

 it is necessary to employ an ioduret in which the phosphorus at most 

 does not exceed a ninth part. The method which I employ is to 

 put the ioduret into a small crucible, and to moisten it with a little 

 water, or what is better, with water already impregnated with 

 hydrionic acid. We may employ likewise a small bent tube. We 

 begin by putting the iodine into this tube ; then reversing it over 

 mercury, we drive out the air which it contains, by introducing a 

 glass rod which almost fills it. The phosphorus is then brought in 

 contact with the iodine, by introducing it through the mercury. 

 As soon as the contact takes place, the two substances combine, 

 and we collect the gas which is disengaged, by putting the extre- 

 mity of the tube under a glass jar standing in the mercury.* 



As soon as the hydriodic gas comes in contact with mercury, it 

 is decomposed. The surface of the metal is covered with a green- 

 ish yellow substance, which is an ioduret of mercury ; and if the 

 contact is prolonged for a sufficient time, or if we agitate, the 

 hydriodic gas is completely decomposed. The iodine combines 

 completely with the metal, and there remains a volume of hydrogen 

 gas, which is exactly one half of that of the hydriodic gas. 1 have 

 made this gas pass upon zinc and potassium, and the result has 

 always been hydrogen gas and an ioduret. From this analysis, and 

 the phenomena which iodine exhibits with hydrosulphuric acid, 

 (sidpkureted hydrogen), and those of the ioduret of phosphorus 



• Wlien distniing a mixture of hydriodic acid and an iodnret of phosphorus, 

 (made without any determined proportions,) in order to obtain the hydriodic acid, 

 towards the end of the operation cubic crystals were formed in the neck of the 

 retort ; they were white, and as transparent as wax. On hot coals they burnt 

 jiiie phospliorus. When put into water, they were instantly decomposed, with a 

 copious discbarpe of subphosphureted hydrogen gas, and allowing flocks of phos- 

 phorus to precipitate. The water coiitained hydriodic arid. Concentrated sul- 

 phiiiic acid, into lyhich these crystals were plunged, became brown, as happens 

 when it decomposfi hydriodic acid. But it soon became reddish ycllovt' and 

 milky, ])robably owing to the phosphorus which precipitated. Iliad too few of 

 these crystals to subject them to more numerous trials and determine exactly their 

 nature. 1 was led to consider them as composed of hydriodic acid and phosphorus, 

 mid ailemptcd to obtain them by passing a current of hydriodic acid gas over 

 phosphorus. I obtained the new compound, but its quantity did not correspond 

 Vith that of the phosphorus and hydriodic acid. Further researchen are necessary. 



