4 Prof. Johnston on the Iodide of a new Carbo-hydrogen. 



case in the previous analysis*. The experimental result 

 however may be reconciled to the formula (C 30 H 20 + H I) 

 which gives 6'340 of hydrogen per cent., a quantity so near 

 to that found as to leave nothing for the ordinary error of 

 analysis. The action of chlorine hereafter described, if the 

 results are to be depended upon, gives a probability to this 

 formula, in addition to that which is derived from the rational 

 formula, adopted by Liebig to represent the constitution of 

 what by other chemists are still regarded as chlorides and 

 iodides of olefiant gas (elayle) and some other carbo-hydro- 

 gens. 



It has been already stated, that when boiled in carbonated 

 alkalies the colour of this compound remains unchanged, 

 and that it undergoes decomposition. The decomposition 

 however is only partial. 4*51 grs. boiled in a concentrated 

 solution of carbonate of soda, and afterwards washed and 

 dried at a gentle heat, still weighed 3*51 grs. having lost 22*17 

 per cent. The whole of the iodine therefore is not separated 

 by this process ; it may however be completely separated by 

 mixture with pure carbonate of soda, and gradually heating 

 over the lamp to a temperature below redness. 



In this way I obtained by means of nitrate of silver an ap- 

 proximation to the quantity of iodine, which however was too 

 rude to be worthy of insertion in the present paper. I was, at 

 the time of making the experiment, unacquainted with the 

 more perfect method of estimating the quantity of iodine since 

 published by Lassaigne. 



II. Diffused through water and subjected to the action of 

 chlorine, the green colour of this compound is slowly changed 

 to brown, but the action is much more rapid and complete 

 when the iodide is reduced to fine powder, diffused through 

 alcohol, and submitted to a current of chlorine. Thus treated 

 it speedily acquires a bright yellow colour, combining with 

 chlorine and yielding the iodine to the supernatant liquid, in 

 which it is readily recognised. 



I subjected to analysis a portion of the substance thus pre- 

 pared, after washing with alcohol and drying at 212° Fahr. 

 When heated in a close tube it gave off no iodine. 



a, 845 grs. gave C = 18*81 grs. and H = 4*545 grs. 



* 2-795 grs. heated to 2)2° for some time, lost 0-295 gr., and at a subse- 

 quent weighing the loss amounted to 0485 gr. Still it seems possible to 

 preserve it for a long time at ordinary temperatures and in close vessels 

 without sensible decomposition. One of the specimens employed in the 

 above analysis was prepared by Mr. Kemp, and had been in my possession 

 several years. 



