My understanding of the von Kossa stain is that it is NOT specific for
calcium.

Rather, the silver nitrate in the staining solution (silver ion is + charge)
binds with the anionic (- charge) portion of the salt. As you indicated, the
von Kossa usually stains calcium phosphate and calcium carbonate, by binding
the positive silver ion with the negative phosphate or carbonate portion.
(Not by binding with the calcium.) This then makes a different silver salt
(silver phosphate or calcium phosphate, for example), which we will see as
black.

In theory, then, von Kossa could also then bind with any other phosphate or
carbonate salt, such as sodium phosphate. In theory, these would also stain
black. However, our bodies usually do not have enough of these other salts
in our bodies to make a positive reaction. So, usually, when we see positive
staining with von Kossa, we assume it is demonstrating a calcium salt.

Also, not all calcium salts give a positive (black) reaction. Calcium
oxalate is thought to not turn black when exposed to silver nitrate. Now,
whether the silver does not bind with the oxalate, or whether the silver
does bind with the oxalate but the new silver oxidate does not turn black,
well, I don't know.

So, in summary, some anions (carbonate and phosphate) do turn black when
exposed to silver nitrate, while others do not (oxalate). In summary, the
von Kossa stain is not specific for calcium, but is specific to the anions
of different salts, but not all salts.

I tried (quickly) this morning to look up the chemical formula for a
tinanate, but couldn't find anything. Obviously, since the tinanate is bound
to calcium, the tinanate is negatively charged. The big questions are:
- will silver ions bind with the tinanate portion
- will silver tinanate be created when calcium tinanate and silver nitrate
are combined
- does silver tinanate turn black so we can see it.

Sorry, I don't know the answers to these. Hopefully, someone else will.

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


----- Original Message -----
From: 
To: 
Sent: Tuesday, January 27, 2004 3:22 PM
Subject: [Histonet] von kossa stain


> hello everyone
> Do you know if does von kossa stain give a positif result with any calcium
> salts ?
>  i think the most common ions are phosphate and carbonates, but if it is
> "calcium titanate" do you think if this  salt is soluble and can give a
positive
> result with von kossa stain ?
> thank you for any help
> Myriam
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> Histonet@lists.utsouthwestern.edu
> http://lists.utsouthwestern.edu/mailman/listinfo/histonet
>


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