BOKON. 175 



For reduction we have the antecedent atomic and molecular weights — 



O := 15-879, ± .0003 Na = 22.881, ± .0046 



Ag= 107. loS, ± .0031 NaCl = 58.060,^.0017 



CI ^ 35.179, zb .0048 AgCl ^ 142.287, rb .0037 

 Br = 79.344, ± .0062 



For the molecular weight of Na.^B^O^ we now have — « 



From (i) Na^B^O, = 200.198, ±: .0377 



From (3) " =z 200.439, ± .0263 



From (4) " =: 200.756, zt .0419 



From (5) " --= 200.260, zh .051 >^ 



General mean Na.^B^O, ^ 200.421, zb .0180 



Hence B = 10.876, ± .0051. 



From ratio (2), B = 10.753, ± .0207. The two values combined give — 



B := 10.863, zb .0050. 



Or, if = 16. B =- 10.946. 



If we consider ratios (1), (3), (4), and (5) separately, they give the fol- 

 lowing values for B : 



From (i) B = 10.821 



From (3) " = 10.881 



From (4).... "^10.960 



From (5) " = 10.836 



Of these, the second and third involve the data from which, in a 

 previous section of this work, the ratio NaCl : AgCl was computed. In 

 using that ratio for measuring the molecular weights of its component 

 molecules, discordance was noted, which again appears here. The chief 

 uncertaint}^ in it seems to be connected with ratio (4), which is therefore 

 entitled to com})arativeh'' little credence, although its rejection is not 

 necessary at this point. In ratio (2), Abrahall's determination, the high 

 probable error of B is due to the also high probable error of 3Br, and it 

 is quite likely that the result is undervalued. The general mean, B = 

 10.863, dz .0050, however, can hardly be much out of the way. It is cer- 

 tainly more probable than any one of the individual values. 



