"Acid-cleaned", now a days, can mean cleaned with a commercially available
product, several varieties, from several companies (maybe they can identify
themselves and their products to you). Or, it could mean the original acid,
known as "aqua regia". (more about this one in a moment)

If a glassware is not washed well after being used with another stain, a
chemical could be left behind on the glassware, such as dye or a metal salt
(ferric chloride for example). Or if the glassware is not rinsed well after
washing, soap would be left behind. Any of these contaminants that are left
behind could react with the silver stain. The silver solution will then
precipitate out, all over your tissue, slide, etc..

The obvious solution is to scrub really well in all the nooks and crannies
and rinse lots of time with d. water. But sometimes even that doesn't get
all the contaminants

To really make certain that all the unwanted left-behind dyes, soap, etc.
are removed, then a strong acid can be used to dissolve away the
contaminants.

The original acid cleaner is "aqua regia", or "royal water". This was the
only solution that could dissolve gold and platinum, the metals that only
really rich people (i.e., royalty) could afford.

Aqua regia is made with 1 part conc. nitric acid to 3 parts conc.
hydrochloric acid. (e.g., 50 mL nitric acid + 150 mL hydrochloric acid) Can
be stored at room temperature in a clear bottle. Can be reused until it
starts taking too long to clean, or turns really dark yellow/orange (it's
light yellowish when first combined).

Pour the aqua regia in the glassware and let it set in the glassware for 1-5
minutes. Pour the aqua regia back into the original bottle.

Slowly add d. water to the glassware (I know, water into acid is a bad idea,
that's why I said slowly). There will be a little white wispy "smoke".

Dump out the d. water, and do several more rinses with d. water. Air drying
is fine, but if you're in a hurry, oven drying would be OK too.

Acid precautions apply = goggle, heavy nitrile-type gloves, store in acid
cabinet, pour away from your face, etc.

Think beyond acid-clean glassware. Ever get a bottle that you just can't get
the dye or chemical out? No matter how hard you scrub or how long you let it
soak or how much bleach you put it? This will definitely get it out. I keep
a bottle of aqua regia in the lab for this purpose. Works great.

Sorry for being a little wordy on this answer.

Peggy A. Wenk, HTL(ASCP)SLS
William Beaumont Hospital
Royal Oak, MI 48073


----- Original Message -----
From: "Diana McCaig" 
To: 
Sent: Friday, August 13, 2004 6:03 PM
Subject: [Histonet] acid washed glassware


> What concentration  and what acid do you use to clean glassware prior to
> silver impregnation staining.  Do you simply rinse it or is it soaked for
a
> specific period of time?  Air or oven dried?
> Diana McCaig, R.T.
> Charge Tech, Histology
> Chatham Kent Health Alliance
> 519-352-6401 (6604)
>
>
> _______________________________________________
> Histonet mailing list
> Histonet@lists.utsouthwestern.edu
> http://lists.utsouthwestern.edu/mailman/listinfo/histonet


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