Pyridylazonaphthol Solution

A 0.1% w/v solution in absolute ethanol.

Complies with the following test.

Sensitivity to copper To 50 mL of water add 10 mL of acetate buffer pH 4.4, 0.1 mL of 0.02m disodium edetate VS and 0.25 mL of the reagent being examined; a yellow colour is produced. Add 0.15 mL of a 0.5% w/v solution of copper(ii) sulfate; the colour changes to violet.