Yes the same.
>
>At a local chemical supply, I was told that ammonium dichromate cannot
>be sold to individuals, because it is explosive. Buying it will not be
>a problem, since I can arrange to purchase it through the community
>college where I will be working on this project. Also, I don't believe
>the small amount that would be on a pot would present a danger to the
>kiln nor to any neighboring pots. What does concern me, however, is the
>possiblity that ignition of the ammonium dichromate would blow the
>pigment off the pot (possibly transferring it to other vessels), thereby
>defeating the purpose of the experiment. So my question is, would
>potassium dichromate give me the photosensitivity without the
>pyrotechnics?
THis is not an explosive but it may bring its oxygen to an explosive to
ease the explosion, let's say. Have a look at what I found on the net and
be aware that these warnings are meant for workers who will handle it in
kilos...
here's the URL:
http://www.chem.utah.edu/MSDS/P/POTASSIUM_DICHROMATE
>
>I have read that the potassium salt is less sensitive than the ammonium
>salt. Can anyone give me an idea of how much difference there is?
The others guys from the list should know it better than me. I would say at
least double.
>
>I have also read that the potassium salt cannot be used with methyl
>alcohol, because the salt precipitates out. Acetone was recommended as
>a substitute, resulting in "an unusually quick-drying sensitizer." Can
>anyone comment on this? Is it possible that an alcohol other than
>methyl would work; in other words, could I have a chance of appearing in
>an Absolut Vodka ad? :-)
Try it but remember tht alcool test for cops are (were) made with potassium
dichromate as an indicator. The potassium dichromate reacts with alcohol
and turn into green potassium chromate (as far as I remember). The coloe
passes from orange to green. For that reaction to take place, you need to
be in an acidic solution (again if I remember well).
>
>All of the processes which use dichromates end with instructions on
>"clearing" the image to remove a yellowish dichromate stain. The
>clearing solution given for the "dusting on" process is a mixture of
>sulfuric acid, water, and methyl alcohol. But for other processes using
>ammonium dichromate, the recommended clearing solution is a 5% aqueous
>solution of either potassium metabisulfite or sodium bisulfite. So:
>Can anyone see any earthly reason to use sulphuric acid?
Potassium metabisulfite is a good choice (from The gum bichromate book of
David Scopick) because it does not alter the colors.
>
>Will the clearing action be the same if the sensitizer is potassium-
>rather than ammonium dichromate?
It depends on their relative solubility I think. Experienced workers will
surely tell you in next mails.
>
>Most important, does the clearing solution actually remove chromium from
>the image, or does it simply change it to a non-yellow form? If the
>chromium is not removed, then the clearing step would be irrelevant in
>ceramics applications.
Yes it is removed because that salt acts as a solubilizer of potaasium
dichromate (and ammonium dich. too)
>
>To those of you who are still reading: Thanks. Any answers will be
>appreciated--but even more appreciated will be any questions I haven't
>thought to ask.
>
>--
>Dennis M. Southwood
>dms1@home.com
>
>
You're welcome
Philippe
-------------------
Philippe Monnoyer
PhD Student in Chemistry
Belgium
-------------------