CHAPTER II. 

 A. THE ATOMIC WEIGHT OF BORON. 



PRELIMINARY EXPERIMENTS. 



In the preliminary experiments one sample of commercial, 

 thrice recrystallized borax was converted into sodium fluoride by 

 a method to be outlined in the following paragraphs, while 

 another sample was changed to sodium chloride by an analogous 

 method. These conversions were made in a platinum crucible of 

 35 c.c. capacity and showed that the method, carried out in this 

 manner, will yield excellent results for ordinary analytical pur- 

 poses. However, irv these instances, ordinary "borax glass" was 

 used, borax which had not been fused to constant weight. There 

 were, of course, other quite obvious reasons why the final deter- 

 minations could not be conducted in a crucible such as the 

 volatility of the halides of sodium (particularly that of the 

 fluoride) and the impracticability of properly applying the "flame 

 test" l for boric acid. 



Three conversions of borax were then effected in the platinum 

 bulb described in Chapter I. In these analyses a special prepara- 

 tion of borax was used (see p. 8); the samples thus analyzed, 

 however, were not considered to be of the degree of purity desired, 

 as they had been removed before the borax was fused and re- 

 crystallized for the final work. These experiments were merely 

 intended to thoroughly test the apparatus and to give practice in 

 the various manipulations involved. It may be added, however, 

 that these three preliminary experiments (in which the borax was 

 dehydrated completely) also supported the low value for boron 

 finally derived. Nevertheless the results, for the reasons just 

 stated, have not been included in table 1 . The final experiments 

 to be recorded in the following pages, therefore, begin with 

 experiment iv, i.e., the first experiment in which the final and 

 best preparation of borax was used. 



In the following description of the individual analyses the 

 number of the experiment refers to the corresponding number in 



1 See note on page 18. 

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