176 THE ATOMIC WEIGHTS. 



(7.) Per cent, of Co in brucia cobalticyanide, 3.7437, ± .0036 

 (8.) " " strychnia " 4- 5705, ± .005 



(9.) Ag : CoCIj : : lOO : 60.2278, d= .Oil 



(10.) Co : H : : lOO : 3.4017, d= .OOO9 



(11.) Au : Co : : loo : 45.151, ± .025 



Hence we have ten values for Co, as follows : 



From (i) and (2) Co = 59.865, ± .0394 



" (4) " = 59.080, zfc .0152 



" (5) " = 58.913, ± .0628 



" (6) " = 59.177, ± .0816 



" (7) " = 59.057, d= .0581 



" (8) :. " = 58.960, ± .0708 



" (II) " = 59.044, d= .0436 



" (9) " =58.961,^.0392 



" (3) " = 58.604, i .0145 



" (10) " =r 58.794, d= .0162 



General mean " ^ 58.887, ± .008 



If = IG, Co = 59.023. 



SELENIUM. 



The atomic weight of this element was first determined 

 by Berzelius,* who, saturating 100 parts of selenium with 

 chlorine, found that 179 of chloride were produced. Further 

 on these figures will be combined with similar results by 

 Dumas. 



We may omit, as unimportant for present purposes, the 

 analyses of alkaline selenates made by Mitscherlich and 

 Nitzsch,t and pass on to the experiments published by Sacc X 

 in 1847. This chemist resorted to a variety of methods, 

 some of which gave good results, while others were unsatis- 

 factory. First, he sought to establish the exact composition 

 of SeOj, both by synthesis and by analysis. The former 

 plan, according to which he oxidized pure selenium by 



* Poggend. Annal., 8, i. 1826. 



t Poggend. Annal., 9, 623. 1827. 



j Ann. d. Chim. et d. Phys., (3,) 21, 119. 



