Natural Science Forum / Physics / Optics / July 2008

Hi all, I have a question I have not been able to resolve through an
exhaustive search and  thought I would give it a try here.

 I am working with histological sections for entomology, heating them and
applying Toluidine Blue .5%, and my sections come out nicely stained, but
all blue.  Meanwhile, I have older slides from someone else to look at which
exhibit a fairly wide and striking color range, from green through blue to
violet-pink, apparently also stained with T Blue.

 Apparently this is known as 'metachromasy' (?) and has something to do
with pH of the stain or fixation, but I cannot find any particulars.  Anyone
know how I can achieve this effect, or a source I can consult?

 Thanks in advance!  =)