SILICON. 105 



O. Pettersson and G. Ekman : 79.08 (O = 16). 



Determined by five analyses of selenious acid. A warm 

 solution of the acid was acidified with chlorhydric acid, 

 precipitated with sulphurous acid and the selenium collected 

 on a glass filter. Many precautions are necessary in the 

 precipitation and drying. The value is the mean ; extreme 

 difierence, 0.04. {Berlin, Bericht der Chem. GeselL, 9, 1876, 

 1212; in extenso in the Acta of the Scientific Soc. of Upsala.) 



SILICON. 



The vexed question of the composition of silicic acid has 

 been settled by H. F. Weber, who found that the specific 

 heat of this element becomes nearly constant above 200° 

 and that the atomic heat is 5.8 for Si = 28. {Poggend. 

 Ann., 154-y 1875, 575.) 



J. J. Berzelius : 39.63 (0 = 16) ; 185.19 (O = 100). 



100 parts of silicon, which had been heated to redness, 

 and freed from silicic acid by hydrofluoric acid, gave 208 

 parts silicic acid, whence the value. Berzelius also made 

 analyses of barium fluosilicide from which he calculated 

 the oxygen contents of the acid at 51.975. This gives for 

 the -atomic weight of Si 29.58. [Poggend. Ann., 8, 1826, 20 ; 

 and Lehrbuch, 3, 1200.) 



J. Pelouze : S8.4.6 (0 = 16 ) ; 177.88 (0 = 100). 



A known weight of perfectly pure silver, dissolved in 

 nitric acid, was brought in contact with a known and slightly 

 excessive weight of silicon tetrachloride and the excess 

 titrated with decimal silver solution. The value is derived 

 from the mean of two experiments; difference 0.76 for O 

 = 100 ; CI = 443.2, Ag = 1349.01. The chloride was pre- 

 pared by Ebelraen ; it was perfectly transparent, volatilized 

 without residue, and had been dried for a long time in a 

 vacuum. [Paris, Comptes Bend., W, 1845, 1047.) 



J. Dumas: 28.02 (0 = 16). 



Determined from the mean of two experiments on the 

 tetrachloride which was weighed off in a glass bulb and 



