SILICON. 85 



From borax B = 10.943, zb .023 



From BCI3 " = 10.808, zb .174 



From BBrj " r= 10.964, ± .364 



General mean " = 10.941. ih .023 



If = 16, B = 10.966. 



Further investigation of the atomic weight of boron is 

 evidently desirable. 



SILICON. 



Although Berzelius* attempted to ascertain the atomic 

 weight of silicon, first by converting pure Si into SiOa, and 

 later from the analysis of BaSiFg, his results were not satis- 

 factory. We need only consider the estimations of Pelouze, 

 Schiel, and Dumas. 



Pelouze,t experimenting upon silicon tetrachloride, em- 

 ployed his usual method of titration with a solution con- 

 taining a known weight of silver. One hundred parts of 

 Ag gave the following equivalencies of SiCl^ : 



39-4325 

 39-4570 



Mean, 39.4447, ±: .0083 



Hence Si = 28.408. 



Essentially the same method was adopted by Dumas.t 

 Pure SiCli was weighed in a sealed glass bulb, then decom- 

 posed by water, and titrated. The results for 100 Ag are 

 given in the third column : 



2.899 grm. SiCl^= 7.3558 grm. Ag. 39-41 1 



1.242 " 3.154 " 39-379 ■ 



3.221 " 8.1875 " 39.340 



Mean, 39.377, it -014 



Hence Si = 28.117. 



* Lehrbuch, 5 Aufl., 3, 1200. 



f Compt. Rend., 20, 1047. 1845. 



J Ann. Chem. Pharm., 113, 31. i860. 



