Staining banded human chromosomes with Romanovsky dyes: some practical consequences of the nature of the stain.

Chromatographic analyses of commercial samples of Romanovsky stains were followed by various chemical and staining studies. Strong banding of chromosomes was found to be favoured by the presence in the stain of high concentrations of methylene violet Bernthsen and its immediate homologues. Chromatographic analysis showed that these dyes are present in dry Leishman and Giemsa powders only in small proportion. However, additional active dye may be generated during the process of making up staining solutions from the dry powders, if the methanol used is not contaminated with formic acid and if the period of heating is not too brief.