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



"With a view to obtain further evidence, I have redetermined with 

 special care the boiling-points, specific gravities, and rates of expansion 

 of the tetrachlorides of silicon, titanium, and tin. 



The atomic weights of Si and Ti and of P and V show about the same 

 gradational difference : — 



Si 28-10 P 31-00 



Ti 50-00 V 51-35 



And since the tetrachlorides are free from oxygen, the uncertainty 

 arising from the variable specific volume of that element is eliminated. I 

 have also compared the specific volumes of the trichlorides of phosphorus, 

 arsenic, and antimony, making use of Kopp's determination in the case 

 of the last-named compound. We thus obtain material for the discussion 

 of the question from analogous derivatives of two well-defined groups of 

 elements, viz. : — 



Si 28-10 P 31-00 



Ti 50-00 V 51-35 



As 75-15 



Sn ...... 118-10 Sn 122*30 



III. Silicon Tetrachloride. 



This compound was prepared in the ordinary way by heating a mixture 

 of pure silica and lampblack (previously ignited in chlorine) in a current 

 of dry chlorine gas. The product was distilled repeatedly over sodium. 

 It boiled constantly between 58° and 58 0, 3, the greater portion coming 

 over at 58°-2. 



Corrected boiling-point 57 0, 95. Bar, 765*35 millhns. Corrected and 

 reduced boiling-point 57°*57. 



Its specific gravity at 0°, compared with water at 4°, is 1-52408. 

 Other observations on record are : — 



Boilin g- Barom. Sp.gr. Compared with 



point. L & water at 4°. 



o millim. . „ 



Pierre* .... 59*0 760*1 1-52371 at 0° 1-52371 at 



Eegnaultf.. 56-81 760-0 . 



Haagent .. 58'0 756*0 1*4878 at 20° 1*52644 „ 



?Mendelejefi e - — - 1-50068 at 10°*98 1-52266 „ 



Mendelejeff§ _ 1-4928 at 15° 1-52230 „ 



Two series of observations of the expansion of silicon tetrachloride 

 were made. The results of the first series may be accurately represented 

 by the formula 



V = 1 + 0-001 337 14 1 + 0-000 002 618 01 1 2 



+ o-ooo ooo 003 907 ea* 8 . . . . (i.) 



* Ann. de Chim. et de Pkys. xx. [3], p. 26. 



t From vapour -tension observations. \ Pogg. Ann. cxxxi. p. 117. 



§ Jahresberieht, xiii. p. 7. - 



