BORON AND FLUORINE. 37 



commercial borax, in which it probably exists as a boro-silicate. 

 If an appreciable quantity of it had been present in the borax 

 used 6 the analyses involving the use of hydrofluoric acid would 

 have yielded a low weight for the end-product and, hence, a high 

 atomic weight for boron; whereas the analyses not involving the 

 use of hydrofluoric acid would have led to an end-product too 

 high in weight and, hence, to a low atomic weight for boron. A 

 glance at table 1 (p. 42) will show that both categories of analysis 

 gave fairly concordant values. The difference between the results 

 obtained in the present experiment (vt) and experiment xi, for 

 example, is practically negligible, although it is only the latter 

 determination which involves the use of hydrofluoric acid. 



Furthermore, it may be gathered from this experiment (vi) 

 that no appreciable quantities of sodium fluoride were lost in the 

 other experiments, when this salt was fused, for the sulphate 

 obtained directly leads to a result in fair agreement with those 

 in which the sulphate had been obtained by the transposition of 

 the fused fluoride. In general, therefore, the result of experiment 

 vi seems to form a rather severe check upon the analyses which 

 included the formate and fluoride of sodium as intermediate 

 products. 



EXPERIMENT VII: THE RATIO OP SODIUM TETRABORATE TO SODIUM NITRATE. 



The procedure followed in this experiment was analogous to 

 the scheme outlined in the other determinations. The borax, 

 fused to constant weight, was dissolved in a little water and the 

 boric acid set free by the addition of an excess of pure nitric acid. 

 The mixture was evaporated to dryness and subjected to a number 

 of distillations with methyl alcohol until free from boric acid. 

 The residue was redissolved in water, evaporated to dryness, and 

 again treated with several portions of methyl alcohol. This series 

 of operations was repeated once more; occasionally a drop of 

 nitric acid was added to the alcohol. A grand total of 56 grams 

 of methyl alcohol was used in this experiment. 



After the evaporation of the last portion of alcohol the residue, 



8 In the present instance it is only from the sodium carbonate used that any silica 

 might have been introduced into the borax. However, the method used for the 

 purification of the sodium carbonate has been found to remove silica quite 

 effectively. 



