A Micromethod for the Determination of Uronic Acids*

The original macromethod of Tollens and Lefevre (1) for the determination of uranic acids has undergone various modifications in the hands of different investigators (2--g). All of t,he modifications are based on the principle that the simple uranic acids and the complex polyuronide substances yield carbon dioxide quant.itatively when distilled with 12 per cent hydrochloric acid. In some the carbon dioxide is determined gravimetrically, in others by tit,rimetric methods. The size of the sample used varies between the limits of 0.2 to 1.0 gm. and the period of heating from 4 to 8 hours. Recently Buston (9) described a micromet.hod embodying titrimetric technique for the determination of uranic acid anhydride groups in pectic subst,ances. In conjunction with t,he studies on the carbonyl sugar acids in progress in this laboratory, one of us (K. P. L.) and a collaborator1 were engaged with the development of a satisfactory micromethod for their determination prior t,o the time of the appearance of Buston’s method. The details had not been completely worked out, consequently it appeared advisable to evaluate the merits a.nd defects of Buston’s method in conjunction with our work. Buston’s method is open to criticism. The apparatus is very