Microdetermination of sulfate in environmental samples
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A new indicator, 2-(8-hydroxy-3,6-disulfo-l-naphthylazo)-l,8- dihydroxynaphthalene-3,6-disulfonic acid (which is called Beryllon II or DSNADNS) has been discovered and is proposed for microtitrimetric determination of sulfate with barium. The procedure is an order of magnitude more sensitive (limit of detection is 0.25 ppm) and less interference prone compared to previously used indicators. The color change is sharper and faster compared to thorin. The optimum conditions involve titration in 80% isopropanol at an apparent pH of 3.5. The superiority of the indicator is attributed to the lower solubility of the barium-dye salt. Results are presented for environmental samples and compared to values obtained by Ion Chromatography. Also, the use of beryllon II in its form of the barium salt for colorimetric determination of sulfate provides a promising result.