Suitable for use in EDTA zinc titration C31H28N2O13SNa4 M.W. 760.59 This substance has been specifically tested for its Suitability in EDTA-zinc titrations. Solubility 0.1%Clear reddish / Violet solution (0.1N NaoH) Absorption max 575 - 580 nm Absorptivity 1% / 1cm min 550 Loss on dying at 105oC(1 hr) max 7.0% Sensitivity for zinc passes test