SILICON. 



189 



filtrate the chlorine was estimated as AgCl. One hundred parts of AgCl 

 correspond to the quantities of SiCl^ given in the last cohinm : 



.6738 grm. SiCl^ gave 2.277 grm- AgCl. 

 1.3092 " 4.418 " 



29.592 

 29.633 



Mean, 29.6125, ± .0138 



Thorpe and Young * working with silicon bromide, seem to have ob- 

 tained fairly good results. The bromide was perfectly clear and color- 

 less, and boiled constantly at 153°. It was weighed, decomposed with 

 water, and evaporated to dryness, the crucible containing it being finally 

 ignited. The crucible was tared by one precisely similar, in which an 

 equal volume of water was also evaporated. Kesults as follows, with 

 weights at vacuum standards : 



9.63007 grm. SiBr^ gave 1.67070 SiO.^. 

 12.36099 

 12.98336 



9.02269 " 

 15.38426 



9.74550 



6.19159 



9.51204 

 10.69317 



The ratios now available are- 



17 



349 per cent. 



.0027 



(i.) 4Ag : SiCl^ : : 100 : 39.4265, ± .0071 

 (2.) 4AgCl : SiCl^ : : 100 : 29.6125, i .0138 

 (3.) SiBr^ : SiOj : : 100 : 17.347, ± -0027 



Reducing these ratios with — 

 O = 15.879, ± .0003 



Ag =r 107.108, zh .0031 



CI ^ 35.179, d 



Br = 79.344, 

 AgCI = 142.287, 



.0062 

 .0037, 



we have the following values for the atomic weight of silicon : 



From (i) Si = 28.200, ± .0363 



From (2) " ^ 27.823, ± .0810 



From (3) "= 28.187, zh .0122 



General mean Si 



28.181, ± .0114 



If = 16, Si = 28.395. 



*Journ. Chem. Soc, 51,576. 1S87. 



