54 THE ATOMIC WEIGHTS OF 



borax the atomic weight of boron may be calculated from the 

 expression : 



M , 286.674X70.646, orB==1L061 . . . (n) 

 100 



These two results differ by 0.11, or fully 1 per cent., an error 

 which can not be accounted for entirely by the solubility of silver 

 chloride or the non-observance of the modern precautions in this 

 precipitation. 8 Nor can it be due to residual boric acid in the 

 sodium chloride, for the method pursued by those authors does 

 not differ radically from that used in the present communication 

 and, as carried out by them, may safely be assumed to lead to a 

 quantitative elimination of the boric acid. 9 In fact, such errors 

 as these, although probably not entirely absent, may be disre- 

 garded for the present. It is the gross errors, errors of the first 

 magnitude, which should be ferreted out first. For similar reasons 

 the etching of the glass vessel (mentioned by Ramsay and Aston), 

 though by no means negligible, need not be considered. It is 

 safe to assume that the silver chloride (which was collected in a 

 Gooch crucible and finally dried at 200) was determined with a 

 tolerable degree of accuracy. If this be granted we shall be 

 enabled to dispel the mystery surrounding the above inconsistent 

 values. 



It has been observed that fused borax, as prepared by Ramsay 

 and Aston, invariably retains water. They had what, for the sake 

 of convenience, has in this paper been termed "borax glass," i.e., 

 vitreous borax, insufficiently fluxed for the complete removal of 

 water. This point should be stated with emphasis. The sodium 



* The present writers do not underrate the importance, in such work, of the solubility 

 of silver chloride. However, it is highly probable that Ramsay and Aston worked 

 with too concentrated solutions, and under such conditions silver chloride invari- 

 ably occludes appreciable quantities of other salts (see Richards and Wells, 

 Carnegie Inst. Washington, Pub. No. 28, p. 31 et seq.) . In other words, these two 

 errors would have balanced each other, to some extent at least. In view of the 

 much more sejious and obvious errors, soon to be discussed, it seems permissible 

 to assume that the solubility of silver chloride in Ramsay and Aston's work is 

 relatively unimportant. 



'According to our interpretation, Ramsay and Aston do not "admit" (see Brauner's 

 criticism in Abegg's Handbuch III (1), p. 7 (1906)), that the conversion of borax 

 into sodium chloride was incomplete, but merely consider it as a contingency, 

 as "not improbable," in their own words, solely in an attempt to account for 

 the discrepancy between the two results derived from the ratios Na 2 B 4 07 : 2NaCl 

 and Na 2 B 4 O7 : 2AgCl, respectively. 



