X814.] On Iodine. 107 



rouriatic acid does to chlorine. The action of phosphorus on iodine 

 furnishing the means of obtaining ihe new acid in its gaseous and 

 liquid sta-e, we shall begin by describing it. 



If we bring dry iodine and pliosphorus in contact, we obtain a 

 matter of a reddish brown colour, itnd no gas is disengaged, if we 

 moisten this matter, it gives out immediately acid fumes in abund- 

 ance, while at the same time phosphorous acid is forined. We 

 easily obtain the new acid in the gaseous state by employing iodine 

 a little moistened. There is then sufficient water to occasion its 

 formation, but not to condense it. if we combine the phosphorus 

 and iodine under water only a little suljphosphureted hydrogen gas 

 is disengaged, and the water becomes very acid. If the new sub- 

 stance is in excess, the liquid is strongly coloured reddish brown ; 

 but it is colourless when the phosphorus exceeds. There commonly 

 remains a mass of a red colour, which refuses to dissolve in water, 

 and in which both phosphorus and iodine may be found ; but the 

 proportions of the two ingredients may be such that the whole 

 dissolves in water without any residue, and the liquid in that case 

 is limpid, like water. 



If we distil the acid liquid, the vi^ater at first is disengaged, and 

 the new acid does not pass into the receiver till the liquid in the 

 retort becomes very concentrated : at last nothing remains in the 

 retort but phosphorous acid, which soon disengages almndance of 

 phosphureted hydrogen gas. Thus it appears that, when the phos- 

 phorus and iodine are dry, there is formed a combination analogous 

 to that of oxymuriatic acid and phosphorus; and when tliey are 

 moist the same thing takes place as when the liquid of phosphorus 

 is thrown into water. Hence it would appear that while the oxygen 

 of the water unites with the phosphorus and forms phosphorous 

 acid, its hydrogen combines with the iodine and forms the new acid. 

 The following are the characters of this new acid. In the 

 gaseous state it is colourless, has nearly tiie smell of muriatic acid, 

 smokes when in contact with air, is rapidly absorbed by water, 

 gives with oxymuriatic gas a b-autiful purple vapour, and is rapidly 

 altered when allowed to remain over mercury. With tlii? metal it 

 forms a greenish yellow substance, similar to that which is ol)tained 

 directly with mercury and the vapour of iodine, while a quantity of 

 liydrogen gas is evolved equal in volume to one half the volume of 

 the acid gas. A few minutes' agitation is sufficient for the entire 

 decomposition. Iron and zinc produce asimilai- eflect. 



This acid in the liquid state, obtained by dissolving the gas in 

 water, forms a very dense liquid, and not very volatile. It rapidly 

 decomposes the alkaline cari)onates, dissolves iron and zinc, with 

 the disengagement of hydrogen gas ; but does not attack niercurv, 

 even when assisted by heat; a proof of the strong affinity which it 

 has for water. It forms with barytes a soluble salt, and gives with 

 corrosive sublimate a red precipitate, soluble in an excess ol the 

 ucid. VViien a few drops of oxynmriatic acid are adtled to it tiie 

 bubbtance is imuicdiutely regeucrutcd. Heated with ibc black 



