Baron wrote:
"Joe" wrote in message
...
On 7 Apr 2006 08:47:26 -0700, wrote:
Don Sforza wrote:
I recently scored some pattern-grade Honduras Mahogany and have a
couple of
projects planned. Not being a "stain everything and slather it with
poly"
guy, I wanted to try potassium dichromate. In a word... holy cow. OK
that's
two words.
A word (or a few) of caution.
Potassium dichromate is a powerful human carcinogen and a strong
oxidizer. For the former reason it has almost entirely been phased out
of industrial uses.
You might be confusing this with another potassium compound.
I assume he refers to K2Cr2O7 which is useful in photographic
processing among other uses, and, as a matter of fact, is the active
ingredient in an over-the-counter headache remedy...cannot remember
the name.
Basically it is an oxidizer.
It is probably illegal to dispose of it by pouring it down the drain.
Though you are not likely to get prosecuted, that is really not
the point.
Probably it would be prudent to do a little reasearch and find a
way to treat it to make it safer for disposal. That _may_ be as
simple as mixing it with portland cement and then throwing
the solid chunk into the garbage.
Perhaps a real chemist can comment further.
I read, in a book on router techniques, of a similar process
using nitric acid. One wets the wood and then heats it with
a heat gun until the desired darkening is achieved, then neutralizes
with a sodium bicarbonate (baking soda) solution. That
process generates nitrogen dioxide which can be quite deadly,
but neutralizing and disposing of the unused solution is
quite trivial.
As with most of life's hazards, there is no rational reason to
be afraid to try these things, one just needs to understand the
dangers and how to mitigate them.
As a "real" chemist, I can tell you that K2Cr2O7 is potassium bichromate
(or dichromate, whichever you prefer). It is a highly corrosive poison.
I'd love to know the source of your statement that it is in a headache
remedy. Chromium in all it oxidation states has been found to be
carcinogenic. It is a matter of its physical form and how you are exposed
to it. Please keep in mind that arsenic and selenium are also necessary
trace elements. I wouldn't go around eating arsenic and chromium salts by
the handful.
As for using it to stain wood, there is no reason to do so. These type
of things were used long ago before the advent of modern light fast stains.
If the old-timers had modern stains, I am sure they would have used them in
preference to "chemical" stains.
I would be careful about using nitric acid to stain wood. A nationally
recognized expert in finishing used some once on a test block of wood.
Several years later, he cut through the piece. He was surprised by the
extent of penetration and how he could still smell the by-products of the
nitric acid. Disposal of nitric acid, while easier than chromate salts, is
not trivial. It must be carefully neutralized and the resulting nitrate
salts must be dealt with.
Must be an old chemist to call in bichromate.
Nonetheless I certainly agree with your statements
on chromium. Don't agree with your statement on
arsenic being an essential trace element.
Nitric acid disposal may be a problem but only for
industrial use, especially if it is contaminated
with dissolved metals which it often is in
industry. Nitrates and nitrites are a problem
when they leach into groundwater but the problem
is mostly from agriculture (excess fertilizers and
stock waste). At least in small amounts the
natural nitrogen-- nitric--nitrate cycle in the
soil will take care of nitric acid. Depending on
where you live, soils will quickly neutralize
nitric acid, plants will take up the nitrates and
soil organisms will change the excess to nitrogen
gas.