Potentiometric titration of fulvic acids from lignite, in dimethylformamide and dimethylsulphoxide media.
Potentiometric titrations in dimethylformamide and dimethylsulphoxide have been performed in order to differentiate between the acidic groups of fulvic acids. With dimethylformamide as medium the best results have been obtained with potassium hydroxide as titrant, whereas both potassium hydroxide and tetrabutylammonium hydroxide yield good titrations in dimethylsulphoxide. The number of acidic groups differentiated depended on the solvent and titrant used; in the best case four sharp end-points were obtained. Titrations with potassium hydroxide are preferred.
Andres
J M
JM
Instituto de Carboquímica, C.S.I.C. Pza. Paraíso No. 1, Ap. 589, 50004-Zaragoza, Spain.
Romero
C
C
Gavilan
J M
JM