BORON AND FLUORINE. 3 



borax, a well-crystallized salt of moderate solubility, represents 

 a definite atomic aggregate seems reasonably certain. That 

 anhydrous borax, although obtained with some difficulty, is no 

 less definite, is practically non-hygroscopic, and may be weighed 

 with ease, will be shown in the sequel. The other salts, namely, 

 the chloride, fluoride, sulphate, nitrate, and carbonate of sodium, 

 have all met with more or less application in atomic weight work. 

 Of these the sulphate was found to be the most stable at the 

 fusion temperature and left practically nothing to be desired 

 when fused in a jacketed vessel. The fluoride, in spite of its high 

 melting-point (at 980), was somewhat volatile; but when heated 

 in the bulb (soon to be described) could be fused to constant 

 weight with comparative ease. Other precautions observed in 

 the heating of these salts will be given in their appropriate places. 

 The completeness of the reaction, i.e., the complete expulsion 

 of boric acid, was tested for, in two cases by means of the flame 

 spectrum; in others, with turmeric paper by both methods with 

 negative results. Indirectly the completeness of the reaction may 

 be inferred from the following considerations: If a number of 

 samples of borax had been converted, by identical operations, 

 into only one kind of salt, e.g., sodium chloride, mere concordance in 

 the results would not necessarily prove that the elimination of boric 

 acid had been complete; under such conditions constant errors 

 are not unknown to have made their appearance. In the present 

 instance, however, borax was converted into a number of different 

 salts, involving a variety of operations and great diversity in condi- 

 tions. A fair concordance obtained by the latter method would 

 indicate that the elimination of boric acid must have been complete. 



DISTILLED WATER. 



Ordinary distilled water was redistilled with a little potassium 

 permanganate made alkaline with potassium hydroxide. The 

 first third of the distillate was rejected. The portion collected 

 was redistilled with a little potassium bisulphate. The product 

 was then redistilled twice. A block-tin condenser was used. The 

 water was stored in well-seasoned flasks of resistance glass, pro- 

 vided with caps fitted on the outside of the neck to prevent con- 

 tact of the water with ground surfaces. 



The seal between the distilling flask and the metal condenser 



