86 Proceedings of Indiana Academy of Science 



hydroxyacids, which increased the conductivity of boric acid. The pres- 

 ent work was undertaken, therefore, having as its object the determina- 

 tion of the possibility of using any of the substances just mentioned in 

 the titration of boric acid. 



Apparatus and Materials, — As in the previous work, the Wendt 

 Electro-titration apparatus was used, with the same electrodes and 

 hydrogen purification train. Moreover, the boric acid and sodium 

 hydroxide solutions were the same as previously described. The organic 

 reagents were used as purchased, inasmuch as conditions simulating 

 those of an industrial laboratory were desired. 



Procedure. — Except in the case of lactic acid, the procedure consisted 

 in the titration of a definite volume of the boric acid solution to which 

 a weighed quantity of the organic substance had been added. In order 

 to have the various titrations on a comparable basis, a definite ratio 

 of four molecular weights of the polyphenol to one of boric acid was 

 maintained. This was modified, in the case of the acids, to one equiva- 

 lent weight of the organic acid to one of boric acid, the reason for 

 the change being given under the discussion of the results obtained. 

 Phenolphthalein was present in each titration, this indicator being the 

 one generally used in volumetric determinations of boric acid. Errors 

 due to temperature changes and to the ab.sorption of carbon dioxide are 

 neglected in view of the purpose of the work. 



Experimental Data. — Although the original data are not included, 

 the curves, plotted from these data, are shown. The usual methods 

 are employed in the plotting of these curves, the pH values being the 

 ordinates and milliliters of standard base the abscissas. The curve for 

 boric acid alone has been repeated on each figure in order that the 

 effect of the organic substance on the neutralization curve can be visual- 

 ized. The curve for the titration in the presence of mannitol is also 

 shown on figure 1, an effect similar to that of mannitol being the 

 desirable effect. 



Polyphenols. — The polyphenols selected were pyrocatechol, 

 o-C„H,(OH)., and pyrogallol, 1, 2, 3-C„H:(0H):,. The work of Boeseken' 

 indicated that the difference between the conductivity of the mixture 

 and the sum of those of the components (KxlO"") was in the case of 

 glycerol, 9; mannitol, 685; pyrocatechol, 516, and pyrogallol, 573. Judg- 

 ing from these data alone, it would appear that the polyphenols promised 

 an efficiency approaching that of mannitol and far in excess of that 

 of glycerol. In the acid range, as indicated in figure 1, the results of 

 the titrations were as expected, but upon approaching and passing the 

 neutralization point, the expected upward break in the curve did not 

 take place. With pyrocatechol, a yellowish-brown coloration develope;! 

 during the titration, masking the color change of the indicator. A 

 decided downward drift was noted in the readings of the millivolt- 

 meter if the solution was allowed to stand after completing the titration. 

 Similar developments were noted with pyrogallol. 



Hydroxyacids. — Of the various acids which Boeseken found to in- 

 crease the electrical conductivity of boric acid, .some are recognized 



■•Ber., J,6, 2612 (1913). 



