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



The numbers representing the specific volumes of the trichlorides of 

 phosphorus, arsenic, and antimony exhibit a gradational order similar to 

 that shown by the volumes of the tetrachlorides of silicon, titanium, and 

 tin, and also by the specific volumes of phosphoryl and vanadyl trichlo- 

 rides : — 



Mol. weight. Spec. vol. 



PC1 3 137-38 93-54 



AsCl 3 181-53 94-64 



SbCl 3 228-68 97-82 



although the differences are much less than in the cases of the two latter 

 groups. I intend to return to the question in subsequent communica- 

 tions. 



II. " Researches upon the Specific Volumes of Liquids. - " By T. 

 E. Thorpe, Ph.D., F.R.S.E., Professor of Chemistry in the 

 Yorkshire College of Science, Leeds. Communicated by Prof. 

 A. W. Williamson, For. Sec. U.S. Received February 9, 

 1876. 



III. On the Specific Volumes of Bromine and Iodine Monochloride, 

 and of Ethene Bromide and Ethene Chloriodide. 



The molecular weight of bromiue is, as is well known, nearly equal to 

 the arithmetic mean of the molecular weights of chlorine and iodine : 

 hence the molecular weights of bromine and of iodine"monochloride (I CI) 

 are nearly identical. These substances closely resemble each other in 

 physical properties. Both are dark-red liquids about three times heavier 

 than water. Bromine boils at about 59°-5, and solidifies at — 24°- 5 ; 

 iodine monochloride melts at -J-24°-5, and boils at 101°: the interval 

 between the boiling- and melting-points of the two compounds is approxi- 

 mately equal. 



It appeared to me of interest to determine (1) if the specific volumes 

 of these liquids exhibit a relation similar to that which is shown by their 

 molecular weights, and (2) if the relation in their specific volumes is 

 preserved in analogous combinations of the two bodies. I have accord- 

 ingly determined the specific gravities, boiling-points, and rates of ex- 

 pansion of bromine and iodine monochloride, and of the compounds 

 which these substances form by their union with ethene, C 2 H 4 . The 

 observations will also serve to determine if bromine and iodine mono- 

 chloride preserve, when in combination, the volumes which they possess 

 in the free state. 



I. Bromine. 



About a kilogramme of the purest commercial bromine, dehydrated 

 by agitation with pure and strong sulphuric acid, was carefully distilled, 

 and the fraction boiling at about 60°, which amounted to about two 



