Re: Technical Grade Muriatic Acid

From: "Christina Z. Anderson" <zphoto@montana.net>
Subject: Re: Technical Grade Muriatic Acid
Date: Sun, 09 Oct 2005 21:35:38 -0600

> I have in my possession sulfuric, phosphoric, and nitric acid (aside
> from glacial acetic). I have been cleaning out my chems and my
> darkroom this weekend in order to set it up, and I am a bit leery of
> these three...I am thinking of disposing of them at the chemistry
> lab at the college, because in all that I do alt process, I have not
> needed them as I thought I might.

These acids are very corrosive and very dangerous if they come to
contact with skin, eyes, mucous membrane, etc. Proper disposal of
these acids requires simple neutralization. Use all common lab safety
measures. The acids should be diluted by adding the acid to a large
amount of water first. Then sufficient amount of washing soda (sodium
carbonate) should be added to make neutral or slightly alkaline pH. If
you have an indicator stop bath, add a bit of that to make the
solution visibly yellow, and add the washing soda until the color
turns purple. If you have a pH test strip or meter, aim pH of 6 to
9. Once neutralized this way, those acids are safe to go down the
drain. If this is too much, you could give them to chemical disposal
companies as well.

Those acids should be stored in a separate chemical cabinet made with
proper nonmetal materials, and should be clearly labeled "acid." You
should also be prepared for accidental spill. Baking soda (sodium
bicarbonate) is commonly used to neutralize the spill in situ.

When a strong acid is needed in darkroom, a convenient alternative is
sulfamic (amidosulfuric) acid, which is supplied in dry form and
therefore presents less risk during transportation and
storage. Technical grade sulfamic acid is readily available as a
cleaning agent for boiler, grout, etc. where calcium carbonate or
phosphate deposits need to be removed. Sulfamic acid is more expensive
than other mineral acids but this acid is less corrosive to metals. As
the low corrosion p[roperty suggests, sulfamic acid is good in
providing low pH but it's no good when making aqua regia...

Sulfamic acid should be dissolved when used, and storage of stock
solution is not recommended because sulfamic acid in aq. solution
slowly decomposes and changes acidity.
Received on Tue Oct 11 03:16:38 2005