Spectrophotometric Determination of Magnesium(II) with 3-Hydroxy-3-m-Tolyl-1-p-Nitrophenyltriazene

Abstract

3-Hydroxy-3-m-tolyl-1-p-nitrophenyltriazene has been used for

the spectrophotometric determination of Mg(II). Magnesium forms

a 1 : 2 (Mg : R) acetone soluble, cherry colour, complex with the

reagent. The complex shows maximum absorbance at 530 nm. At

working wavelength 560 nm, ε = 11,500 L mole^–1 cm^–1. For constant

maximum colour development Mg : R was 1 : 6 and pH was

between 10.4-10.8. Values of molar absorptivity, Sandell's sensitivity,

stability constant (log β) and free energy of formation were

found to be 11,500 L mole^–1 cm^–1, 0.21 ng/cm² ,11.00 and -15.101

kca/mole respectively. Beer's law is obeyed in the entire concentration

range studied, i.e., 1.0 x 10^–6 M to 6.0 X 10^–6 M. It was possible

to determine magnesium (0.12 ppm) in presence of two-fold molar

excess of ninteeen cations and anions.