On Thu, 9 Dec 1999, Lesley Weston wrote:

> Does anyone happen to remember the recipe for rhodanile blue? I've lost
> mine and can't find it on the net either. Thanks.

  My short answer is, "No, I've not got the recipe," but Lesley's
  enquiry raises some interesting points.  How much is this stain
  used, for what purposes, and with what success?

  This was a concoction of Edward Gurr ("Encyclopaedia of Microscopic
  Stains" and various other books). The following notes are from
  long-term memory and Lillie's 10th edition of Conn's Biological
  Stains (1977), which is to hand. Lillie cites MacConnail & Gurr,
  Irish J. Med. Sci. 1964: 243-250 for the seminal work on rhodanile
  blue. I haven't seen this paper, but have made a note to look it
  up.

  It seems likely that Gurr mixed a cationic dye (nile blue) with an
  amphoteric (but predominantly cationic) dye, rhodamine B. He published
  a formula, presumably speculative, that implied the formation of
  an amide from the -COOH of rhodamine B and the -NH2 of nile blue, to
  make a cationic xanthene-oxazine hybrid dye. This is chemically
  improbable if the parent dyes were combined in aqueous solution, and
  it is very much more likely that solutions contain coloured cations
  of rhodamine B (red), nile blue (blue) and perhaps also some nile
  red, which is a hydrophobic product of oxidation of nile blue.
  Lillie (1977) reviewed 4 or 5 published applications of rhodanile
  blue, but gave no indication of how the results were influenced by
  such things as the pH solvents during and after staining.

  Edward Gurr published other dye mixtures as "compounds," notably
  FALG (and FALGOG). These contained acid fuchsine ("fuchsinic acid"
  in Gurr's terminology) with light green (and orange G). They were
  touted as one-step multicolour reagents. I tried these soon after
  Gurr's "Encyclopaedia" came out, but could get only grey-violet
  shades with the occasional bright red cell or unrecognizable blob.

  Please don't interpret the preceding paragraphs as an attack on the
  memory of the late Edward Gurr, who sold good stains and wrote good
  books. ("When I am dead let it be said, That his sins were scarlet
  but his books were read." - Hillaire Belloc)  Perhaps some
  HistoNetter older than I will tell us more about the saga of the
  Brothers Gurr.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1
   E-mail: kiernan@uwo.ca