[Histonet] Re: difference in hematoxylins

[Robert Richmond]

I think we've gone over the terminology of alum hematoxylins more than
once on Histonet.

When you make up a working solution of what we call hematoxylin, you
dissolve the colorless dyestuff (dye precursor) hematoxylin in water.
With oxidation the colorless dyestuff becomes the dye, called hematein
(though this word is rarely used). The hematein deteriorates, forming
the iridescent scum on the surface and the precipitate that adheres to
the glass.

The aluminum (alum) serves as a mordant, attaching the dye to the
material to be dyed. Glycerol, ethanol, chloral hydrate, ethylene
glycol, and similar additives serve primarily as preservatives. The
acid (traditionally acetic) determines a lot of the staining qualities
of the mix, and determines whether a regressive step (partial
decolorization in acid after hematoxylin staining. Do NOT put this in
my frozen section sequence!) is needed.

How the oxidation is done determines the usual terminology of hematoxylins.

Delafield's hematoxylin: loosely stopper the newly prepared
hematoxylin and leave it under the sink for a few months. Atmospheric
oxygen slowly accomplishes the oxidation.

Harris's hematoxylin: heat the solution almost to boiling and add
mercuric oxide.

Mayer's hematoxylin: oxidize at room temperature with sodium iodate.
(Mayer rimes with liar, not with layer.)

Because of present day restrictions on mercury in the laboratory,
Harris's hematoxylin is probably out of manufacture, and making it
yourself is not a good idea.

The new Good Management definition of Harris's hematoxylin is "any
alum hematoxylin our marketing department wants to call Harris
hematoxylin." It's sometimes labeled as not containing mercury.

The Gill hematoxylins are (or once were) Mayer-type hematoxylins, with
a rationalized recalculation of the formula that goes back to J.T.
Baker (Cytologic Technique, 1960, if I remember correctly). If Gary
Gill is still on Histonet, he can elaborate.

Proprietary hematoxylins today are probably oxidized either with
sodium iodate or with oxygen. This doesn't matter to the user.

With any brand of hematoxylin that's new to you, you have to work out
a staining sequence that works for you. This should be done with the
input of your pathologist or researcher. Unfortunately, most
pathologists and researchers know very little about these matters, and
information on the subject isn't easy for them to get.

Bob Richmond
Samurai Pathologist
Knoxville TN