1904.] Physical Characters of the Sodium JBorates, etc. 291 



Melting point. 



Composition of mixture. Glass. Crystals. 



B 2 O 3 468 



Na 2 0.40B 2 3 470 



Na 2 0.16B 2 3 528 



Na 2 0.4B 2 3 628 858 



Na 2 0.2B 2 3 628 791 



9Na 2 0.16B 2 3 613 



5Na 2 0.8B 2 3 620 777 



3Na 2 0.4B 2 O 3 610 815 



Na 2 O.B 2 O 3 615 930 



5Na 2 0.4B 2 3 960 



5Na 2 O.4B 2 3 + Na 2 C0 3 917 



5Na 2 0.4B 2 O 3 + 3Na 2 C0 3 ... 783 



5Na 2 0.4B 2 3 +4Na 2 C0 3 ... 654 



5Na 2 0.4B 2 3 + 5Na 2 C0 3 ... 664 



5Na 2 0.4B 2 O 3 + 6Na 2 C0 3 ... 692 



5Na 2 O.4B 2 3 + 7Na 2 C0 3 ... 685 



5Na 2 O.4B 2 O 3 + 27Na 2 C0 3 ... 722 



We have analysed a number of the glasses and crystals obtained 

 with various mixtures, and obtained most unexpected and interesting 

 results. 



The analysis of a borate is always a matter of difficulty, but we 

 found the following method worked quite well, and gave accurate 

 results. A weighed quantity of the substance (glass or crystals in 

 very fine powder) was evaporated to dry ness twice with fairly strong 

 hydrochloric acid. By this means all the sodium was 'converted into 

 the chloride. The dry powder thus obtained was repeatedly treated 

 with small quantities of methyl alcohol, and evaporated to dryness. 

 By this means all traces of hydrochloric acid were removed, as well as 

 the whole of the boracic acid, so that pure sodium chloride remained. 

 This was dissolved in water and estimated by titration with N/10 silver 

 nitrate solution, using potassium chromate as indicator. 



The complete separation of the crystals from the glass was by no 

 means an easy matter. We found that quite the easiest and most 

 satisfactory method was to crush up the substance into coarse powder, 

 and then to pick out with forceps the really glassy fragments and the 

 crystalline masses. This was quite easy by using a lens. 



Though the crystals and glass have different specific gravities, it 

 was not found possible to obtain a real separation by means of a 

 heavy liquid. This was because pieces of material which looked 

 wholly crystalline often contained glass in the interior, so that they 

 would float anywhere in the liquid. 



We also tried extraction with hot methyl alcohol which is a solvent 



