BORON AND FLUORINE. 



13 



mechanical loss. It is scarcely necessary to add that evaporation 

 of solutions was always carried out at a temperature much below 

 the respective boiling-points. Nevertheless, traces of dissolved 

 air, upon being expelled on warming, may cause serious loss, 

 which will be en- 

 tirely prevented by 

 these plates. Finally 

 these perforated 

 disks serve to pre- 

 vent a flame at the 

 mouth of the bulb 

 from "striking 

 back." As will be 

 explained later, the 

 alcoholic vapors ex- 

 pelled in the volatil- 

 ization of boric acid 

 were ignited from 

 time to time. 



The method of 

 supporting the bulb 

 during the experi- 

 ment is indicated in 

 the sketch. Two 

 stout lugs, diamet- 

 rically opposite and 

 fused to the upper 

 part of the neck, 

 rested on the prongs 

 of a fork made of 

 heavy platinum 

 wire. The advan- FIG. 4. 



tages of this device 



over any other method of support are too obvious to be detailed. 

 The flange of the cup-shaped stopper, carrying the inner tube, 

 rested on a similar fork. The forks were independent of each 

 other, but they were permanently set into appropriate clamps 

 which could be adjusted in the usual manner. 



The elbow (dbc) served to connect the inner tube to the con- 



