There are two plans available for this purpose; one is a dyeing test, the other is a colorimetric test made with the solutions of the dyes.
"The Dyeing of Woollen Fabrics"
Franklin Beech
When this test is used as a colorimetric method for the estimation of chlorine several difficulties are encountered; the intensity of the colour produced by the majority of treated waters gradually diminishes and the loss is usually more rapid than in the standards made up with distilled water; a different result is obtained if the solutions are acidified and the results vary with different acids, acetic acid yielding a much lower result than a mineral acid such as hydrochloric acid; in the presence of acid the colouration usually intensifies on standing, whereas the standard intensifies but little.
"Chlorination of Water"
Joseph Race