280 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



The ratios for silicon are now — 



(1). 4Ag:SiCl,: :100:39.4265, ± .0071 

 (2). 4AgCl:SiCU: : 100:29.6125, ± .0138 

 (3). SiCl,:SiO,: : 100: 35.4145, ± .0017 

 (4). SiBr,:SiO„: :100:17.347, ± .0027 



Reducing these ratios with Ag=107.880,±. 00029, Cl = 35.4584,± 

 .0002, and Br =79.9197, ±.0003, we have— 



From ratio 2 Si = 27.9516, ± .0792 



" 3 28.2257, ± .0045 



" 1 28.2996, ± .0307 



" 4 28.3785, ± .0115 



General mean. Si =: 28.2462, ± .0041 



The rounded-off mean, Si = 28.25, is probably as near the truth as any 

 of the individual values. 



TITANIUM. 



The earliest determinations of the atomic weight of titanium are due 

 to Heinrich Rose.' In his first investigation he studied the conversion 

 of titanium sulphide into titanic acid, and obtained erroneous results; 

 later, in 1829, he published his analyses of the chloride.^ This compound 

 was purified by repeated rectifications over mercury and over potassium, 

 and was weighed in bulbs of thin glass. These were broken under water 

 in tightly stoppered flasks ; the titanic acid was precipitated by ammonia, 

 and the chlorine was estimated as silver chloride. The following results 

 were obtained. In a fourth column I give the TiO, in percentages 

 referred to TiCl^ as 100, and in a fifth column the quantity of TiCl^ 

 proportional to 100 parts of AgCl : 



Mean, 42.933, ± .121 33.156,±.019 

 Hence Ti = 48.262, from column 5. 



' Gilbert's Annalen, 1823, 67 and 129. 



- Poggend. Annalen, 15, 145. Berz. Lehrbuch, 3, 1210. 



