BORON AND FLUORINE. 19 



It seemed entirely possible that this final loss was due to the 

 volatilization of boric acid. It is true, Abrahall had shown that 

 up to 265 no volatilization of this component took place during 

 the expulsion of water of crystallization. This observation, how- 

 ever, gave no clue as to what might take place at or above the 

 fusion temperature. As any possible trace of boric acid could not 

 conveniently be tested for directly, under the conditions, the entire 

 question was disposed of by the following simple experiment. 



A sample of "borax glass," weighing 1 gram, was fused in the 

 platinum flask in a stream of dry air until its weight was constant. 

 A small quantity of pure water was then added and the contents 

 digested at a gentle heat for many hours. The water was finally 

 evaporated very slowly and the residue again fused to constant 

 weight. The latter was 0.026 milligram in excess of the final weight 

 recorded just before the evaporation with water. In other words, 

 the two final weighings before and after the treatment with water 

 were identical, for the apparent difference found did not exceed 

 the experimental error in weighing. It should be added that the 

 second dehydration of the borax required fully as much time and 

 effort as the first. This experiment seemed to justify the conclu- 

 sion that, by the method indicated, borax can be completely 

 dehydrated without any loss of the salt itself, that no boric acid 

 is volatilized with the water, and that the final loss sustained by 

 borax glass upon fusion is due entirely to the removal of the last 

 traces of water. 



In some experiments it was found that the borax had actually 

 begun to vaporize within the bulb, for a distinct film of fused 

 borax was noticeable on the end of the inner platinum tube; how- 

 ever, as the long neck of the bulb remained comparatively cool, 

 no weighable quantities of the salt had left the apparatus. This 

 water, it should be added, was not hygroscopic water, which 

 might have been taken up just before the substance was trans- 

 ferred to the bulb, but represented the last portion of the original 

 water of crystallization. Pure borax glass was found to be prac- 



of narrow-bore nickeled brass tubing and was kept scrupulously clean. Such a 

 flame was also used occasionally to ignite the vapors escaping from the bulb in 

 the final treatment of the residues with methyl alcohol. Crude as it may seem, 

 this method of testing proved quite satisfactory and, as carried out, precluded 

 the possibility of contaminating the contents of the bulb. 



