418 Mr. J. F. W. Johnston on Iodic JEthcr. 



for several days, and a little more iodine added as the colour 

 slowly disappears. The addition of a little sulphuric a3ther 

 will at any time by agitation give a solution of the iodic in com- 

 mon aBther, which floating on the top may easily be separated. 



The supernatant acid liquid in the first process contains a 

 large quantity of iodine in solution, partly in the state of aether, 

 partly, probably, as Faraday's iodide of aetherine, and partly 

 as Serullas's periodide of carbon. The aether is not wholly 

 separated by subsidence on cooling ; a further portion is thrown 

 down by the addition of water, and a second portion by satu- 

 ration with an alkali, though in both cases slightly coloured. 

 Agitation with sulphuric aether separates it most completely. 

 Saturated with soda the supernatant liquid becomes dark co- 

 loured, and by evaporation may be brought to a treacly con- 

 sistence, but does not crystallize. The dark colour is not due 

 alone to free iodine, for it does not disappear by long ex- 

 posure to the air, nor by heating, but to carbon, which exists 

 either in a peculiar state of combination with iodine, or as 

 ulmic or azulmic acid. By evaporation to a syrup, and sub- 

 sequent dilution with cold water, a carbonaceous matter is se- 

 parated, which is soluble in hot water, and in solution throws 

 down a yellow iodide from the salts of lead. Alcohol does 

 not separate the iodine from this carbonaceous matter, but it 

 may be driven off by the heat of a spirit-lamp, leaving a spongy 

 charcoal. 



When the acid liquid is diluted and supersaturated with 

 ammonia a yellow precipitate falls, which is chiefly Serullas's 

 periodide of carbon. This compound is sometimes obtained 

 also on decomposing the aether by dry caustic potash. Nitric 

 acid throws down iodine from the filtered ammoniacal solu- 

 tion, and by evaporation it becomes dark coloured as above 

 stated. The saturated supernatant liquid does not precipitate 

 chloride of barium. 



What is the true constitution of this interesting compound, 

 it is difficult to decide. From the mode in which it is formed 

 by the aid of nitric acid we should be led to infer the presence 

 of oxygen ; while, on the other hand, its properties and the ab- 

 sence of iodic acid, both in the caustic alkaline solution by 

 which it has been decomposed, and in the supernatant liquid, 

 which even when saturated gives no precipitate with muriate 

 of barytes, lead to a contrary conclusion. When iodic acid 

 is heated in alcohol decomposition takes place, and by distilla- 

 tion the whole of the iodine passes over, the odour of hydriodic 

 aether, which is perceptible, showing that a small quantity of 

 that compound has also been formed. The presence of alco- 

 hol, therefore, in a hot solution, seems incompatible with an 



