ATOMIC WEIGHTS 



279 



.6738 grm. SiCl^ gave 2.277 grm. AgCl. 29.592 

 1.3092 " 4.418 " 29.633 



Mean, 29.6125. ± .0138 



Hence Si = 27.952. 



Thorpe and Young/ working with silicon bromide, obtained better 

 results. The bromide was perfectly clear and colorless, and boiled con- 

 stantly 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. Eesults as follows, with vacuum weights: 



9.63007 grm. SiBr, gave 1.67070 SiO,. 



12.36099 " 2.14318 " 



12.98336 " 2.25244 " 



1.56542 " 



2.66518 " 



1.69020 " 



1.07536 " 



1.65065 " 



1.85555 " 



9.02269 

 15.38426 

 9.74550 

 6.19159 

 9.51204 

 10.69317 



17.349 per cent. 



17.338 



17.349 



17.350 



17.324 



17.343 



17.368 



17.353 



17.353 



0027 



Mean, 17.347, 



Hence 81 = 28.379. 



The determinations by Becker and Meyer ^ resemble the foregoing 

 series, except that silicon tetrachloride was used instead of the bromide. 

 The carefully purified substance was decomposed by water, the solution 

 was evaporated to dryness, and the silica produced was weigbed. In a 

 second communication Meyer " discusses the possible retention of chlorine 

 by the silica, and shows that that error was avoided. The data obtained 

 by Becker and Meyer follow, with vacuum weights, and a percentage 

 column computed by myself: 



4.69585 

 4.91918 

 5.37434 

 5.93985 

 6.73605 

 7.16361 

 7.82779 



Mean, 35.4145, ± .0017 



Hence Si = 28.226. 



iJourn. Chem. Soc, 51, 576. 1SS7. 

 ^Zeitsch. anorg. Chem., 43, 251. 1905. 



'Zeitsch. anorg. Chem., 46, 45. 1905. In Vol. 43, p. 242, Meyer discusses the problem of the 

 calculation of atomic weights. 



