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



Pierre represents the expansion of this liquid by the equation* : — 

 V= 1 + 0-001 132 800 769* + 0-000 000 911 710 706-* 2 



+ 0-000 000 007 579 789*", 

 which gives results somewhat lower than those afforded by formula III. 



20°. 40°. 60°. 80°. 100°. 



Pierre.... 1-02308 1-04726 1-07289 1-10034 1-12998 

 Thorpe .. 1-02347 1-04771 1-07340 1-10080 1-13024 



The specific volume of tin tetrachloride, calculated from Pierre's obser- 



. 259-94 1000 ^ 

 rations, is ^^^3 = 132-371. 



The results of the determinations of the specific volumes of the tetra- 

 chlorides of silicon, titanium, and tin, liquids of analogous constitution 

 and all derivatives of the tetrad group of elements, serve to establish the 

 conclusion, indicated by the difference in the specific volumes of phos- 

 phoryl and vanadyl trichlorides, that the specific volumes of the several 

 members of a family of elements are not identical, but that the values 

 increase with the increase of the atomic weight of the members. 



Molecular Specific 



weight. volume. 



SiCl 4 169-94 121-13 



TiCl 4 191-84 126-03 



SnCl 4 259-94 131-41 



It is also noteworthy that the difference between the specific volumes 

 of tin and titanium tetrachlorides is almost the same as the difference 

 between the specific volumes of vanadyl and phosphoryl trichlorides ; it 

 has already been remarked that the difference between the atomic weights 

 of vanadium and phosphorus is nearly the same as that between the 

 atomic weights of titanium and silicon. 



Mol. weight. Biff. Spec. vol. Diff. 



?OCl 3 153-38 101-58 



VOCl 3 173-73 ^ dD 106-54 4 yb 



SiCl 4 .> 169-94 121-13 



TiCl 4 191-84 ' JU 126-03 4 yu 



It would seem from this that the constitution of vanadyl trichloride is 

 similar to that of the phosphoryl compound, and must therefore be ex- 

 pressed by the formula 



CI 



- V— O— CI 



I 

 CI, 



in which V appears as a triad, the oxygen atom having the same specific 



* Log. cit. p. 20. 



