Alizarin S Solution

A 0.1% w/v solution of alizarin S.

Complies with the following tests.

Sensitivity to barium To 5 mL of 0.05m sulfuric acid add 5 mL of water, 50 mL of acetate buffer pH 3.7 and 0.5 mL of the solution being examined. Add, dropwise, 0.05m barium perchlorate VS. The colour changes from yellow to orange-red.

Colour change pH 3.7 (yellow) to pH 5.2 (violet).