378 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



SILICON. 



Although Berzelius' attempted to ascertain the atomic weight of 

 silicon, first by converting pure Si into SiO,, and later from the analysis 

 of BaSiFg, his results were not satisfactory. We need consider only the 

 work of Pelouze, Schiel, Dumas, Thorpe and Young, and Becker and 

 Meyer, 



Pelouze,' experimenting upon silicon tetrachloride, employed his usual 



method of titration with a solution containing 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 = 28.373. 



Essentially the same method was adopted by Dumas.* Pure SiCl4 

 was weighed in a sealed glass bulb, then decomposed by water, and 

 titrated. The results for 100 Ag are given in the third column : 



2.899 grm. SiCl,== 7.3558 grm. Ag. 39.411 



1.242 " 3.154 " 39.379 



3.221 " 8.1875 " 39.340 



Mean, 39.377, ± .014 - 



Hence Si = 28.080. 



Dumas' and Pelouze's series combine as follows: 



Pelouze 39.4447, ± .0083 



Dumas 39.377, ± .014 



General mean 39.4265, ± .0071 



Schiel,* also studying the chloride of silicon, decomposed it by am- 

 monia. After warming and long standing it was filtered, and in the 

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

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



'Lehrbuch, 5 Aufl., 3, 1200. 

 2 Compt. Rend., 20, 1047. 1845. 

 » -\nn. Chem. Pharm., 113, 31. 1860. 

 *-4nn. Chem. Pharm., 120, 94. 



