CONGO RED AS AN INDICATOR FOR MAGNESIUM: I. A COMPARISON OF SERUM VALUES USING CONGO RED AND TITAN YELLOW

Abstract

Congo red was successfully substituted for titan yellow in the colorimetric estimation of magnesium in serum by using 50 μg/ml congo red as the working standard (i.e., halving the dye concentration), and by determining the optical density at 560 mμ in a Beckman DU spectrophotometer.Thirteen serum samples were obtained from 12 healthy subjects, and the magnesium in each sample was estimated with both congo red and titan yellow to provide a comparision of the methods. The mean values obtained by these methods were: 1.95 mg/100 ml or 1.61 meq/l. with congo red, and 2.15 mg/100 ml or 1.77 meq/l. with titan yellow.