On Wed, 24 Mar 1999, Gayle Callis wrote:

> Question:  dye used for amyloid staining, called Rit scarlet No. 5
> per publication in J Histotechnolgy, March 1999.
> 
> Looking for the company or supplier who makes it, CPC Speciality Markets
> USA from Indianapolis IN.  Phone, email, address will be appreciated.

  The name RIT goes with packets of dye that you can buy for
  home use, to change the colours of your shirts, undies, towels,
  socks etc. They were around when I was a kid in England in the
  1950s, and they're still here in Canada (1999). Each packet
  has instructions, and information about the colour and the 
  kind of textile it will dye. 

  When I saw the J. Histotechnol. paper I immediately got out my
  trusty Colour Index CD-ROM and tried to look up the dye and the
  RIT company. Result: NOTHING!  There are 2 or 3 dye companies
  with names beginning Rit... but it was not possible to find
  anything resembling the product in the paper, or indeed anything
  that looked like a domestic RIT dye. So we have no idea what 
  rit scarlet no. 5 is, even though it's probably available all
  over the world if you look at the small print on little packets
  of dye in the supermarket.

  Somebody with intelligence and enterprise has found a cheap,
  probably widely available product that can be used to stain
  amyloid. Unfortunately there is no easy way to find out what
  this dye is. It could well be a mixture. Domestic dyeing
  became feasible in the 1890s with the invention of dis- and
  tris-azo dyes that could stick to cellulose (cotton, linen). 
  This is now known to be a property of large dye molecules
  that can align themselves with the macromolecular framework
  of the substrate to be dyed. 

  The staining of amyloid is a diagnostic exercise, undertaken
  by using a dye.  The well documented methodology with Congo
  red sets a standard, but it is not necessarily the best
  technique. Sirius red F3B is one serious competitor for
  Congo red, and there are others. One of these may be a
  dye that's in your local supermarket. For all you can
  know it might actually be Congo red or sirius red F3B or
  any other polyazo dye or mixture of dyes.

  In a clinical/legal horror setting, who can afford to say 
  to the judge:

        I read it in an article in a scientific journal
   but the article didn't state the name of the dye I
   used to test for amyloidosis, or give any other
   information about what it was.

  Therefore until the identity of this dyestuff is discovered
  its use for diagnostic purposes seems unwise, however
  effective the staining method seems to be. Similarly, this
  stuff could not reasonably be used in research because
  a refereed journal would want proper identification of
  the chemicals used in the work.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1