304 Mr. T. E. Thorpe on the [Feb. 17, 



He also selected the volume at 20°* 09, the lowest temperature at which 

 he made an observation, as the unit of volume, on the ground that at 

 lower temperatures, particularly in the neighbourhood of its freezing- 

 point, the dilatation of the liquid might be irregular, a supposition which 

 is not confirmed by my observations. He accordingly calculated two 

 expressions of the form * 



V= l+aQ + bd 2 + cd\ 



in which = *-2O°-O9. 



From 20 o, 09 to 100°- 16 the expansion may be expressed by the 

 formula 



V= 1 + 0-000 952 696 190 + 0-000 001 316 506 858 a 



+ 0-000 000 001 062 687a 3 ; 



and from 100°-16 to 132°-6 by the formula 



V = l + 0-001 016 765 9880 + 0-000 000 102 231 77O0 2 



+ 0-000 000 008 788 007 3 . 



These formulae give results differing but little from those afforded by the 

 expression deduced from my observations, as is evident from the fol- 

 lowing comparison (the temperatures are given in degrees of the 

 mercurial thermometer) : — 



20°-09 



50° 09 



80°-09 



110°-09 



130°-09 



. 1-00000 



1-02980 



1-06213 



1-09709 



1-12238 



. 1-00000 



1-03003 



1-06230 



1-09750 



1-12284 



Pierre . 

 Thorpe 



The specific volume of ethene dibromide, calculated from the numbers 

 given by Pierre, on the assumption that the specific gravity of the liquid 

 at 20°- 79, viz. 2-16292, as given by him, is compared with water at 4° 

 (the temperature of comparison is not stated, but it is probably that 

 which is assumed), is 97*7. 



IV. Ethene Chloriodide, C 2 H 4 IC1. 



This remarkable compound was first prepared by Maxwell Simpson. 

 To obtain it, finely powdered iodine is suspended in about three times 

 its weight of water, and chlorine is passed into the liquid (which should 

 be kept cool and constantly agitated) until the iodine has nearly disap- 

 peared ; the liquid is decanted after standing, and a stream of ethene, 

 washed by passing through soda solution, is led into it until both the 

 liquid and the oil which gradually separates out are decolorized. The 

 compound, after washing and drying, is found to boil nearly constantly. 

 "When first prepared it is colourless ; but on exposure to light it gradually 

 becomes red from the separation of a trace of iodine f . 



In order, if possible, to avoid the use of water in the preparation of 

 this compound, I attempted to obtain it by the direct addition of pure 



* Loe. cit. t Proc. Roy. Soc. xi. p. 590, xii. p. 278. 



