2 Prof. Johnston on the Iodide of a new Carlo-hydrogen. 



light carburetted and olefiant gases, are present. The 

 latter would furnish the three compounds obtained in this 

 experiment, as shown by the following formula : 



2 (C 2 H 2 ) + 5 I = H I + C 2 H 2 1 + C 2 H I 3 



that is to say, one atom of olefiant gas decomposes to form 

 hydriodic acid and formyle, while another unites with iodine* 

 directly. Still this does not represent the action qaanti- 

 tively, since the proportion of the C 2 H 2 I is much greater in 

 actual experiment, and appears also to be variable. 



Such is the action in close vessels provided only with a 

 small aperture to allow the current of gas to pass out very 

 slowly ; but since these three compounds are all volatile, it is 

 easy to understand how only the solid dark green fixed sub- 

 stance should be obtained when the iodine is placed in an 

 open vessel and a current of coal gas is made to stream upon 

 it. In this way it was first obtained by Mr. Kemp of Edin- 

 burgh, to whom the discovery of this substance is due, and 

 who several years ago presented me with a specimen prepared 

 by exposing iodine for several days to the action of an open 

 jet of coal gas. I am not aware how far Mr. Kemp has since 

 studied the action in close vessels. 



I. This substance is of a dark olive green colour, is with- 

 out taste, emits a slight odour of naphtha, is brittle, and has 

 a density of about 0*95. It Is insoluble in water, and in boil- 

 ing alcohol or aether. Treated with hot nitric acid it becomes 

 yellow and dissolves. With muriatic acid either in the form 

 of gas or of liquid acid, it undergoes no change. Sulphuric 

 acid aided by heat decomposes it. It blackens and gives off 

 iodine vapour and sulphurous acid, leaving undissolved a very 

 bulky charcoal. Dry chlorine slowly changes its colour to a 

 dark brown. If previously moistened with alcohol it becomes 



* During the combination of chlorine with olefiant gas a portion of 

 muriatic acid is formed, a fact inconsistent with the idea of a direct union 

 of the two substances to form H 2 C 2 CI : may not an equivalent proportion 

 of the volatile chloroform be produced, as in the above formula, substi- 

 tuting CI for I ? Felix d'Arcet {Ann. de Chim. et de Phys., lxvi. p. 108.).has 

 stated, that during this action of chlorine on olefiant gas, a second oily 

 liquid is formed, represented by C 4 H 4 CI O, to which he gives the name 

 of chloretheral, but which Berzelius with great probability I think, consi» 

 ders to be a compound of the chloride with the oxide ofelayle (C 2 H 2 CI 

 + C 2 H 2 O). This explanation of the production of muriatic acid, how- 

 ever, implies that the gases employed are always more or less moist. Re- 

 gnault accounts for the presence of the acid by representing the oily com- 

 pound by the rational formula (C 2 H 3 C1 + H CI) part of which is decom- 

 posed during the process, and H CI evolved. But Ldwig and Wiedman 

 have shown that C 2 H 3 (acetyle) does not preexist in the oil, though it 

 may possibly be formed by its decomposition. See Poggendorft's Annale?i t 

 xlix. p. 133. 



