Titrimetric estimation of mercaptosuccinic acid.

Abstract

Mercaptosuccinic acid (MSA) was detd. by titrn. with Fe(ClO4)3 (prepd.by dissolving Fe(OH)3 in HClO4 and standardized by gravimetric estn.of Fe). Thus, a standard soln. of MSA was run into Fe(III) soln.,which was acidified (2N) with HCl or H2SO4. An intense blue colordeveloped as the titrn. progressed and disappeared at the end point.The indirect titrn. was carried out by adding Fe(III) soln. to MSAsoln. (end point was the appearance of a blue color) also gave satisfactoryresults. One g.-ion of Fe(III) reacted with 2 moles of MSA. The reactioninvolved the redn. of Fe(III) to Fe(II), oxidn. of MSA to a disulfideand the formation of a 1:1 Fe(II)-MSA complex, λmax. 234 mμ. Thecompn. was detd. by the method of continuous variation at pH 4 andconfirmed by potentiometric titrn. Log K, the formation const. was4.531 at 25°. [on SciFinder(R)]