CHAPTER I. GENERAL PART. 

 PRINCIPLE OF THE METHOD. 



According to Rosenbladt, 1 the characteristic green color 

 imparted to an ordinary alcohol flame by boric acid was known 

 to Geoffrey in 1732. In course of time it was found that this 

 test became more delicate when methyl alcohol was used. In 

 1887 Gooch 2 and Rosenbladt, 3 both working independently, 

 successfully adapted this qualitative test to the estimation of 

 boric acid, which until then had presented great difficulties to the 

 analyst. 4 In order to estimate boron in a soluble borate, for 

 example, it was merely necessary to liberate the boric acid by the 

 addition of a stronger acid, and then expel the former as its methyl 

 ester, by repeated evaporations with methyl alcohol, after which 

 the ester was hydrolyzed and the boric acid thus fixed, by a 

 suitable absorbent or "retainer." This general method for the 

 elimination of boric acid from borax, with certain modifications, 

 was also pursued in the present work; the methyl borate, 

 however, was allowed to escape, since the weights of the anhy- 

 drous borax and the residual sodium salt served to establish the 

 desired ratios. 



This volatilization method was first used in atomic weight 

 determinations by Ramsay and Aston, 6 who distilled borax with 

 hydrochloric acid and methyl alcohol and weighed the residual 

 sodium chloride. 



Rosenbladt expelled the boric acid in the presence of sulphuric 

 acid. Gooch, according to his original communication, found it 

 difficult to choose between acetic and nitric acids. As the esteri- 

 fication of boric acid is counteracted by water, it is readily seen 

 that the latter should be absent, or nearly so, unless a vast excess 

 of methyl alcohol be used. For such reasons the use of acetic 



1 Z. anorg. Chem. 26, 18 (1887). 



*Chem. N. 55, 7 (1887). 



1 Loc. cit. 



4 More recent modifications in the estimation of boric acid, and additional references, 



may be found in a paper by Wherry and Chapin, J. Am. Chem. Soc., 30, 1687 



(1908). 

 6 J. Chem. Soc. 63, 211 (1893). 



1 



