Titration of Boric Acid 



87 



at once as belonging to the group known as hydroxyacids, such as lactic, 

 tartaric, etc. Others showing a positive effect, such as oxalic and malonic, 

 one would not so classify. Boeseken has explained the action of the 

 latter by assuming that we have to do with a polyhydroxy-compound 

 formed by the hydration of the carboxyl group at the carbonyl oxygen 

 so that the OH groups are favorably situated. Several members of 

 each of these types of acids were selected. 



In titrating boric acid in the presence of another acid stronger 

 than itself, one would expect a pH curve quite different from those 



13 

 It 

 II 

 10 

 9 

 8 



6 

 5 



3 

 Z 

 I 



II 16 ZO a 28 32. 



ml of OZ A^ Na Oh 



fO 44 



Fig. 1. 

 polyphenols 



Titiation of boric acid (.',0 ml. ol' a solution 0.0994 N) in the presence of 

 (1) acid alone, (2) pyiocatechol, (3) pyrogallol, (4) mannitol. 



obtained in titrating boric acid in the presence of a polyalcohol. In 

 the latter case boric acid is the only constituent being neutralized, and 

 the general effect of the polyalcohol is to produce a complex acid more 

 highly ionized than boric acid. This effect becomes apparent in a con- 

 siderable drop, along the pH scale, of the initial portion of the neutraliza- 

 tion curve and in the appearance in it of a comparatively long vertical 

 portion. The titration of a mixture of boric and lactic acids, for ex- 

 ample, is a different matter. In studying the electrical conductivity 

 of such a system Boeseken had merely to prepare a given mixture and 

 then to determine whether its conductivity differed from the value cal- 

 culated as the sum of the contributions of each constituent to the total. 



