RE: [Histonet] pHing of eosin

From:Gary Gill

Re dye content variation in biological dyes certified by the Biological
Stain Commission, eosin must contain at least 90% dye to be certified.  The
threshold used to be 80% until about 1996 or so.  Dye content is printed on
the labels of all certified dyes -- a notable exception being hematoxylin,
as it is not a dye per se.  The amount of dye that should be weighed out to
produce the same total dye content (TDC) solution will vary, therefore.

For example, to prepare 1 liter of 0.5% TDC eosin solution (raw dye content
= 90% [0.9]), dissolve 5.55 gm eosin in 1 liter solvent (i.e., 5 gm =F7 0.9 =
5.55 gm).  If the raw dye content were 95%, one would weigh out 5.26 gm
(i.e., 5 gm  0.95 = 5.26 gm).  A difference of 0.29 gm will not make any
visually appreciable difference.

If one were using dyes with lower certification dye content thresholds, the
differences between a corrected and uncorrected amount of dye could be
visibly appreciable (e.g., light green SF yellowish = 65%, orange G =3D 80%).

Gary Gill

-----Original Message-----
From: Barry R Rittman [] 
Sent: Monday, August 16, 2004 6:37 AM
Subject: FW: [Histonet] pHing of eosin

I believe that care should  be used in universally adding  specific amounts
of acetic acid to acidify eosin solutions that differ. 

	I asume that different batches of dye have different dye contents so
that the 5% stain that one user prepares is a little different from that
used by others. Each lab should prepare their eosin with this is mind.
	I usually add a low percentage of acetic acid to the eosin until a
faint opalescence occurs. I have been told that this is the point at which
the dye acid just starts to precipitate. 
	For our eosin solutions this involves 5  drops or so of 2% acetic
acid per 100 ml of 5% eosin.

		-----Original Message----- 
		From: on behalf of
Tony Henwood 
		Sent: Sun 8/15/2004 6:27 PM 
		To: 'Daryl Mikita'; 
		Subject: RE: [Histonet] pHing of eosin

		We use 3% acetic acid
		Tony Henwood JP, BAppSc, GradDipSysAnalys, CT(ASC)
		Laboratory Manager
		The Children's Hospital at Westmead,
		Locked Bag 4001, Westmead, 2145, AUSTRALIA.
		Tel: 612 9845 3306
		Fax: 612 9845 3318
		-----Original Message-----
		From: Daryl Mikita []
		Sent: Saturday, 14 August 2004 5:44 AM
		Subject: [Histonet] pHing of eosin
		We are looking at pHing our eosin to the correct pH, instead
of just using
		it straight from the bottle.  What should we use to adjust
the pH?  Should
		it be 1N sodium hydroxide or  1N hydrochloric acid? 
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