BORON AND FLUORINE. 29 



centimeters of methyl alcohol (see p. 9) and the methyl borate 

 gradually expelled in a current of air. Air proved entirely satis- 

 factory for this purpose and showed no tendency to form explosive 

 mixtures. At first the air-bath (i.e., the outer platinum crucible) 

 was kept at a temperature of about 50, which was raised very 

 slowly. Finally, when no more alcoholic vapors were given off, 

 the temperature was gradually increased to about 110, or even 

 a little higher. 



After cooling, the evaporation was repeated several times with 

 fresh portions of methyl alcohol. In each evaporation 5 to 8 c.c. 

 of the alcohol were used and a drop of formic acid was added to 

 the last portions. The best indication as to the progress of this 

 volatilization of the boric acid could be obtained by igniting the 

 vapors, from time to time, at the mouth of the bulb (see note 

 on p. 18). The flame was easily extinguished again by interrupt- 

 ing the air current for a moment. As long as any considerable 

 amount of methyl borate was present in the vapors, the flame 

 showed the familiar green coloration. It is evident that the 

 delicacy of this color reaction depends not only on the amount of 

 boric acid present, but also on the relative amount of alcohol 

 used. However, it was found that the presence of about 0.1 per 

 cent, of boric acid could be detected in sodium formate by this 

 flame test when only small quantities (2 to 3 c.c.) of methyl 

 alcohol were used. 



When the flame test no longer indicated the presence of boric 

 acid, the contents of the bulb were digested with a few cubic 

 centimeters of water and again evaporated to dryness. The 

 treatment with alcohol was then repeated. The vapors, when 

 ignited, again showed a very faint green at first. Two more 

 evaporations with 2 c.c. of water, followed by treatment with 

 several portions of about 3 c.c. of methyl alcohol, were carried 

 out. Five small portions of alcohol were used in the final evapo- 

 rations. The total quantity of methyl alcohol used in this 

 determination was not noted ; however, it did not exceed 40 grams. 

 In some of the later experiments the exact total was recorded. 



That the residue (sodium formate) after such treatment con- 

 tained no perceptible traces of boric acid was proved as follows 

 (see also p. 3) : Another sample of borax had been converted 

 into sodium formate by the method just outlined. The residue 



