Bacteriological evaluation of two test methods for chlorine in swimming pools.

It was found that orthotolidine and plastic test strips containing a mixture of syringaldazine and vanillinazine gave different results as to chlorine content of water samples containing urine or large amounts of bacteria while giving consistently similar results with water samples having only sodium hypochlorite added. Orthotolidine was found to give erroneously "safe" readings when in fact viable bacteria were observed on membrane filters after filtration.