The adsorption of mixture of methyl blue, eriochrome black-
T and phenol red was also studied on the activated charcoal in
the concentration range 0.05–5 ppm. Weighed amount (0.01 g)
of activated charcoal in a flask containing 25 ml mixed dye solution
was shaken in a water bath incubator (Hitachi BT-47) at
298 K. The solutions were filtered. The concentration of the
remaining amount of each dyes was determined by measuring
the absorbance of the mixture of dyes at their respective λmax and
then applying Beer–Lambert law to calculate the concentration
of each dye. The effect of interference between the colours of
the dye was excluded because the mixture of dyes was scanned
for λmax and only three λmax (eriochrome black-T = 530, phenol
red = 435, methyl blue = 610 nm) were found corresponding to
the individual dyes of the mixture.