Studies on metachromasia. III. Toluidine blue-substrate interaction and metachromasia.

With salts as substrates the metachromatic responses of the thiazine dye, Toluidine blue are studied. It is found that generally salts produce a gamma-metachromatic response. The substrate-dye interaction is studied in detail and the results are discussed in the light of various interpretations of previous workers. It is suggested that toluidine blue may have two sites that are responsible for the exhibition of green and red metachromatic responses. The influence of water on metachromasia has been studied and is reported to bring about an oscillation of spectral colours. Spectrophotometric studies were also carried out.