8 THE ATOMIC WEIGHTS OF 



washed with a small quantity of cold water, previously boiled. 

 The product was recrystallized twice from water free from carbon 

 dioxide and drained and washed as before. In these recrystal- 

 lizations the solution was "inoculated" with a trace of the 

 decahydrate (prepared for the purpose) as soon as the temperature 

 of the solution had fallen a little below 55, which approximately 

 marks the transition point between the penta- and decahydrates. 

 The preparation thus obtained was used in some of the preliminary 

 determinations. 



There seemed to be a remote possibility that this borax was 

 not entirely free from unknown organic derivatives which might 

 have accompanied the boric acid because of its preparation from 

 the methyl ester. While no evidence to this effect could be ob- 

 tained, it seemed best to dehydrate the borax and fuse it to a 

 clear glass before the final recrystallizations. Pure borax from 

 another source had been fused for hours in the platinum dish 

 before it was used for the fusion of the borax in question. 

 Even at the risk of making a rather superfluous statement, 

 mention must be made of the extreme brilliancy of the "borax 

 glass" thus obtained and the total absence of the slightest 

 color from the melt, even when examined "end-on" and in thick 

 layers. 



The "borax glass" was dissolved in water, free from carbon 

 dioxide, and recrystallized four times in the manner and with the 

 precautions already indicated. The product was dried and partly 

 dehydrated over solid potassium hydroxide. The salt, even before 

 the final recrystallizations, contained no perceptible traces of 

 carbonate, for a powdered sample moistened with water and 

 dilute hydrochloric acid remained free from bubbles, even when 

 examined under the magnifying glass. Under the microscope the 

 crystals presented an entirely uniform and homogeneous appear- 

 ance. In some instances the mother liquors were allowed to 

 evaporate to dryness over caustic potash, when nothing but borax 

 (free from carbonate) was obtained. The crystals obtained by 

 spontaneous evaporation of such solutions were remarkably stable 

 and showed no sign of efflorescence, even when exposed for weeks 

 to ordinary atmospheric conditions. 



Reliable tests indicating the presence, in borax, of traces of 

 other borates (either more basic or more acid in character) are 



