BORON AND FLUORINE. 65 



nitrate, and carbonate. The value of such a method is 

 obvious. The atomic weight of boron thus found was 

 10.900, referred to the oxygen standard. 



(7) These data, which included the ratio between sodium tetra- 

 borate and sodium fluoride, were also used for a recalcula- 

 tion of the atomic weight of fluorine which was thus found 

 to be 19.005. 



(8) The new value for boron (10.900) is practically a whole per 



cent, lower than the one at present in use (11.0). It seemed 

 desirable, therefore, to search for the chief cause, or causes, 

 of this discrepancy. As the writers are not aware of any 

 serious flaws in their own determinations, it became im- 

 perative to subject the work of others to a somewhat 

 critical study. A number of palpable errors in such work 

 have been pointed out, chief among which is the retention 

 of water by "borax glass." In the light of this criticism 

 of previous determinations it would seem that the various 

 sources of error had conspired, as it were, in favor of the 

 higher value (11.0) for boron. The evidence, both direct 

 and inferential, collected in Chapter III in support of the 

 lower figure (10.900) seems little short of conclusive. 



(9) It is of particular interest to note that if the present 

 writers had used incompletely dehydrated borax as was 

 done in the past the atomic weight of boron would have 

 been 11.0. This result, though incorrect, is of value in 

 clinching the argument in favor of the new value (10.900). 



(10) It should be borne in mind that the present work, including 

 the discussion of previous determinations, was confined to 

 borax. It has been hinted, however, that the analyses of 

 other compounds of boron, recorded in the literature, also 

 lead to rather uncertain values for boron. A careful 

 analysis of such compounds, particularly of the halides, 

 would be of interest and furnish a valuable check upon the 

 value derived in the present study. 



