论文部分内容阅读
前言黄腐酸是腐植酸中能溶于酸和碱、分子量较小的部分,是结构极不规则的一类天然聚电解质。它们与金属离子的络合作用主要决定于分子中的酸性基团。因此,研究各类酸性基团在溶液中的电离平衡和质子化常数,对深入了解络合作用是十分必要的。黄腐酸各酸性基团质子化常数的测定方法已有报导,但大都是近似求算,不利于进一步计算络合稳定常数。Gamble和Perdue等人曾把腐植酸视为一元酸的混合物。我们认为黄腐酸各酸性基团电离强弱不同,当量数也各不相等,即使同种基团,由于可处部位不同,电荷影响不同,在电离上也有所差异。考虑到这种差异,若把它们作为一元酸的混合酸,则可使腐植酸这类复杂分子电离平衡的处理大为简化。我们根据Briggs和Stuehr对一元和多元酸体系同时电位测定当量点和电离常数(K_2)
Fulvic acid humic acid is soluble in acid and alkali, the smaller the part, is a very irregular structure of a natural polyelectrolyte. Their complexation with metal ions depends mainly on the acidic groups in the molecule. Therefore, studying the ionization equilibrium and protonation constants of various acidic groups in solution is very necessary for understanding the complexation. The methods for the determination of the protonation constants of fulvic acid groups have been reported, but most of them are approximate calculations, which is not conducive to the further calculation of the complex stability constants. Gamble and Perdue et al. Considered humic acid as a mixture of monobasic acids. We believe that each acid group fulvic acid ionization strength of different strength, the equivalent number is also not equal, even if the same group, due to the different parts can have different charge effects in ionization are also different. Considering this difference, if they are mixed acids of monobasic acids, the treatment of the ionization equilibrium of such complex molecules as humic acid is greatly simplified. We measured the equivalent points and the ionization constants (K 2) for the simultaneous potentials of monobasic and polyacid systems according to Briggs and Stuehr