BORON AND FLUORINE. 17 



reliable than those of Leonard, who gives no experimental data 

 besides stating that his conclusions were based upon the titration 

 of borax before and after fusion in a crucible for several hours, 

 and that the residue required less standard acid for exact neutrali- 

 zation than did the original borax glass. Such a titration does 

 not necessarily prove that the portion volatilized had a composi- 

 tion different from that of borax, for, during a protracted ignition 

 over a gas flame, the contents of the crucible might have absorbed 

 appreciable quantities of sulphur dioxide and, as a result, required 

 less acid for neutralization. Waldbott analyzed the residual borax 

 by expelling the boron with ammonium fluoride and weighing the 

 alkali as sodium sulphate. 



Although any possible absorption of sulphur from the flame 

 was also overlooked by Waldbott, it is easily seen that such an 

 error would have had less effect upon his analyses than upon the 

 titrations made by Leonard. However this may be, it is certain, 

 and not at all surprising, that borax can not be kept fused for any 

 considerable time without loss. Our best criterion of complete 

 dehydration is constancy of weight after several ignitions. Obvi- 

 ously this criterion could not be applied to borax which was 

 being fused in an open vessel, such as a crucible or dish the only 

 vessels used in this particular instance in the past. The final 

 dehydration of borax, therefore, was carried out in the apparatus 

 already described, (p. 12). Completely dehydrated borax could 

 be kept fused in this vessel for hours without any loss of the salt 

 itself. A receptacle of this description was also well adapted to 

 the subsequent volatilization of boric acid. 



The general plan pursued in the dehydration of borax may 

 now be given. The pure decahydrate, immediately after centri- 

 fugal draining, was placed in a desiccator containing caustic 

 potash. The latter served the double purpose of protecting the 

 salt from the carbon dioxide of the air and of removing part of 

 the water of crystallization. In some instances it was found that 

 the borax, consisting of a fine crystal meal, had been converted 

 into the pentahydrate by this treatment. The latter salt is better 

 suited for the subsequent expulsion of water, as it does not dissolve 

 in its water of hydration and does not intumesce to such a marked 

 degree as the deca-salt. This salt was placed in a rather capacious 

 (150 c.c.) platinum crucible with a perforated lid, through which 



