Sequential Titration of Calcium and Magnesium in Malt Beverages. Tsing-Chiang Ho and George P. Skocic, J. E. Siebel Sons' Co., Enzyme Products Division, Miles Laboratories, Chicago, IL 60646. J. Am. Soc. Brew. Chem. 39:0041, 1981.

2-Hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid (Cal-Red™) and Eriochrome Black T™ were used as double indicators for calcium and magnesium, respectively, for the direct sequential titration of calcium and magnesium ions in malt beverages. The calcium ion was titrated with ethylenediamine tetraacetic acid (EDTA) at pH 12-14 using the Cal-Red indicator, which has a distinct color change at the end point. The workability of this determination depends on the principle that the magnesium ion is quantitatively precipitated as magnesium hydroxide at pH 12-14 and is not titratable with EDTA under these conditions. After the calcium titration was completed, the solution was adjusted to pH 10±0.1 and the magnesium titrated with EDTA.

Keywords: Beer, Calcium, Cal-Red, Eriochrome Black T, Ethylenediamine tetraacetic acid, Magnesium