84 THE ATOMIC WEIGHTS. 



BORON 



The atomic weight of this element has been determined 

 by Berzehus and by Laurent, and calculated by Dumas 

 from some experiments by Deville. 



Berzelius* based his determination upon three concordant 

 estimations of the percentage of water in borax. Laurentf 

 made use of two similar estimations, and all five may be 

 properly put in one series, thus : 



47.10 I 



47.10 [ Berzelius, 



47.10J 



47-^5 I Laurent. 

 47.20/ 



Mean, 47.13, ifc .013 



Hence B = 10.943, ± .023. 



Dumas'l calculations were based on Deville's analyses of 

 the chloride and bromide of boron, which give the ratios 

 between AgCl and BCI3, and between AgBr and BBy^. Re- 

 ducing the weighings to a common standard, 100 parts of 

 silver chloride correspond to the quantities of boron tri- 

 chloride given in the third column : 



.6763 grm. BCI3 -=. 2.447 grm. AgCl. 27.303 



.923 " 3.395 " 27.187 



Mean, 27.245, rb .0^9 



* Hence B = 10.808, it .174. 



With the bromide, 2.44G BBrj gave 5.496 AgBr. If we 

 assign this experiment equal weight with one in the chlo- 

 ride series, and include the probable error of Br, B = 

 10.964, ±1 .304. 



The three values combine as follows : 



" Poggend. Annal., 8, i. 1826. 



f Journ. fur Prakt. Chem., 47, 415. 18 



J Ann. Chem. Pharm., 113, 31. i860. 



