591 



of iodine, expecting that the teriodide would be formed by virtue of 

 the following reaction : 



C 4 H 4 I 2 +C1I=C 4 H 3 I 3 + HC1. 



My expectations, however, were not realized, the product of the re- 

 action being a body which I shall call chloriodide of ethylene (C 4 H 4 

 I Cl). The experiment was performed in the following manner : 



Action of Chloride of Iodine on Iodide of Ethylene. A solution of 

 chloride of iodine in water containing a trace of free iodine was 

 agitated vigorously with a quantity of iodide of ethylene, till the latter 

 became black and changed into a fluid oil. This was then washed 

 with dilute potash and distilled. Almost the entire liquid passed 

 over between 146 and 152 Cent. It gave, on analysis, results which 

 correspond perfectly with the formula I have given above. I obtained 

 12-43 instead of 12'55 per cent, of carbon. 



If we regard the constitution of iodide of ethylene as C 4 H 3 1, HI, 

 the reaction which gives birth to this body becomes perfectly in- 

 telligible. It is simply the substitution of chlorine for iodine in hy- 

 driodic acid : 



C 4 H 3 I,HI+C1I=C 4 H 3 I,HC1+II. 



Chloriodide of ethylidene is a colourless oil. It has a sweet taste, 

 and is slightly soluble in water. It boils at about 147 Cent. It is a 

 remarkable fact that neither this body nor Dutch liquid is formed 

 when iodide of ethylene is exposed to the action of chlorine-water. 



I have also subjected propylene gas, derived from amylic alcohol, 

 to the action of chloride of iodine, and find that an oily body is formed 

 in large quantity, which contains iodine. This I am at present en- 

 gaged in studying. The action of chloride of iodine on propylene 

 gas obtained from glycerine appears to be similar. 



Letter to the Council from Sir George Everest, C.B., On the 

 Expediency of re-examining the Southern Portion of the 

 Great Indian Arc of the Meridian ; and Report of a Com- 

 mittee thereupon. 



[Towards the close of the last session of the Royal Society a letter 

 was addressed to the President and Council by Colonel Sir George 

 Everest, C.B., advocating the expediency of re-examining the portion 

 of the Great Indian Arc of Meridian which was surveyed by the 



