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neutrino
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>With strong vacuum, about 1 drop every minute came through.
When you filter something that tends to clog the filter, you generally want as low a vacuum as possible. A strong vacuum only drives the clogging
particles deeper into the filter, clogging it even more.
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garage chemist
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I now had great success in distilling the mercury from the amalgams, using a bent test tube made of real Duran glass and not the stuff I got on ebay
where the seller claims that it is.
The mercury I got out equivalented to 99% of the stated mercury content. I had to heat until the amalgams glowed red in order for this yield to be
possible.
If heated too fast, the mercury doesn't condense as drops, but partially as a dark grey dust that refuses to flow together.
The mercury must be distilled slowly, also because the horizontal part of the test tube is only air cooled.
Patience is the key.
The mercury doesn't form a mirror, and doesn't wet the glass, which is good.
After the thing has cooled down, the biggest drop of mercury can be tilted around in the tube and absorbs the smaller drops.
A great thing is that I will get 70g of silver out of the 200g of amalgams, along with the mercury.
I think I'll go to some dentists and ask for old amalgams, as far as I know they are just hazardous waste and have to be disposed of by special firms,
which costs the dentists some money.
If I can get a lot of these amalgams, I could make quite some money by seling the silver (the Hg I'll keep for myself, of course ).
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Lambda
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| Quote: | | Does anyone know how I can clean the filter plate from the SnO2? It must be a chemical method to dissolve the SnO2. |
@Garage Chemist, were you able to use NaOH and HNO3 to clean up your filter plate ?.
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garage chemist
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I used HCl, it dissolved most of the SnO2 and the filter is useable again.
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garage chemist
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I've made some pictures!
Go to http://www.versuchschemie.de/topic,5748,60,-Unfall+beim+Dest...
scroll down a bit and click on the links. The pictures are in chronological order.
As you can see, I further improved the method by not bending the test tube, but only making an "edge" into it to separate distillation material and
distillate. This facilitates removal of the distillation residue (consists mainly of silver).
For everyone not scared of this procedure, I suggest asking for old dental amalgam residues at dentists.
They consist of 35% silver!
You could potentially make a lot of money with this. I know of someone who got more than 4kg of amalgams at a dentistry, which would give him 1,4kg of
silver, with a market value of ca. 400$.
Of course you'd have to build a steel retort (a "pipe bomb" with attached thin steel pipe for drawing off the vapors) for distilling the mercury out
of them (hint: fill it only halfway, the amalgams swell during distillation). It would be placed in a charcoal fire and heated to red heat, and the
vapor tube cooled with water to condense the mercury.
Also, you'd have to have access to cheap 53% technical grade nitric acid for dissolving the silver- bearing metal residues.
Separation would consist in filtrating the solution from the SnO2 and adding HCl to precipitate silver as the insoluble chloride.
The AgCl can be purified by dissolving in ammonia, filtering from residual mercury salts (both sorts of mercury ions form insoluble complexes with
ammonia) and reprecipitation by adding HNO3.
Reduction of the AgCl is achieved by stirring with hot NaOH solution and adding sugar (yes, ordinary sucrose does the job nicely and is the cheapest
reagent for this, I've done it several times).
Melting and casting of the silver would be a problem, due to the large amounts involved and the rather high melting point.
An electric furnace would have to be employed, with a graphite crucible.
[Edited on 23-2-2006 by garage chemist]
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Fleaker
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Have you also considered the presence of palladium in these fillings (Pd fillings are whiter and harder than the norm)? I have some fillings that are
palladium/silver/tin/mercury along with the generic 16K gold ones. You might want to check for palladium ion? I forget the exact test, but I believe
dimethylglyoxime is used to check for the presence, while it can be dropped out with ammonium chloride. I'd be more interested in the palladium
possibility rather than the silver. To me, working with the toxic mercury compounds and fumes does not seem worthwhile just for the silver. Too much
hassle, not enough reward unless you can get a great bulk deal.
BTW, Garage chemist, building a furnace is simple! If you can distill mercury and prepare its solutions and survive, then you can most certainly make
a propane fired foundry that can melt kilograms of anything from aluminum to iron for maybe 140 euros. U2U if you are interested, I have some proven
plans for a small
furnace.
"The AgCl can be purified by dissolving in ammonia, filtering from residual mercury salts (both sorts of mercury ions form insoluble complexes with
ammonia) and reprecipitation by adding HNO3. "
Having used both nitric and hydrochloric acids to accomplish this, I'd suggest using hydrochloric acid as it is both cheaper and easier (no
introduction of NO3- ion). You mentioned the standard organometallic reduction of silver with sucrose (works with dextrose "Karo syrup") and an alkali
base. I normally have to heat this to convert it all over. Another method that works faster is cementation with zinc (just dissolve the excess zinc
in HCl and buchner it).
Either way, nice work! Keep it up and keep it safe
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garage chemist
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No Palladium in the fillings, I have worked with palladium before (also a dental alloy, from which I ultimately recovered 2g of Pd in the form of its
insoluble dichlorodiammin complex which I decomposed to metallic Pd and melted down into a button) and would have immediately recognized its very
strong brown color on dissolution in HNO3 (earlier I mentioned that I have dissolved 20g of the amalgam in order to separate its constituents
chemically, and the solution was just bluish).
Palladium(II) has very strong brown color in solution, even when very diluted the solution is almost opaque (unless it is complexed with ammonia, then
the solution is colorless, but the brown color is immediately seen when dissolving the alloy in HNO3, and the complex is only stable in basic media).
Palladium(IV) is ruby red, also strong color.
On boiling of a Pd(IV) solution, it decomposes to the Pd(II) state (an important characteristic which allows its separation from e.g. platinum).
If you want help with separation of platinum group metals or dental precious metal alloys, ask me. I've worked with several of those before.
BTW, do you have a procedure for the reduction of AgCl with NaOH and sucrose where amounts and concentration of the NaOH are stated? I don't know how
much to use.
Brauer says for this "reduce with sucrose in hot NaOH solution", and this is all I know about this procedure.
I plan on making a furnace at some time in the future, and a propane one would be nice as a first project, but ultimately I want an electric one. They
operate cleaner and the atmosphere inside doesn't contain CO2 and H2O, which can be a problem in some applications.
Suggestions for a propane furnace are still welcome.
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Rosco Bodine
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IIRC the decomposition temperature for mercuric nitrate
is considerably lower than for the more stable silver nitrate . So if you have a nitric acid solution of silver
and mercuric nitrates which you want to separate ,
just evaporate to a residue in a boiling water bath
and continue heating on the bath for an hour or so
stirring the residue with a glass rod occasionally until
you see no more telltale red fumes coming off the mercuric nitrate decomposing to insoluble white mercuric oxide . Then you can add distilled water
and filter out
the mercuric oxide , to get a solution of silver nitrate .
From the silver nitrate you can isolate the silver easily
by any of several methods . If you are doing silver recovery on any substantial scale , this is probably the most efficient way to go .
As a bonus you can recover the pure mercury by dissolving the mercuric oxide in HCl and displacing it from solution with
very pure scrap electrical conductor Aluminum wire , the mercury separates as the free element when the wire dissolves in the solution . The hydrogen
produced from
this may be useful too for some convenient purpose if
you are working on a sizeable scale . And the aluminum chloride has modest value as a byproduct also .
[Edited on 28-2-2006 by Rosco Bodine]
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neutrino
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Does the oxide formed decompose any further at these temperatures? I know that mercury is unusual in that its oxide decomposes at a relatively low
temperature into the free metal.
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Rosco Bodine
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I have never seen any metallic residue accompanying the decomposition and the weight analysis squares with conversion efficiency that is quantitative
within the usual accuracy of ordinary lab scales . If you heated too strongly for too long , then yeah you would lose mercury , but limiting the
operation to boiling water bath temperatures and doing what I describe , the process is better than 99.9% efficient 
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neutrino
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Boiling water? That really is a low decomposition point. The oxide decomposes far above that, in the hundreds of degrees celcius.
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Rosco Bodine
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Yes 100C is plenty . I have done this several times
to make mercuric oxide as an intermediate for
mercuric chloride , starting by dissolving mercury metal
in ordinary 68% HNO3 , evaporating to dryness and
then to decomposition , in a glass bowl sitting in
a boiling water bath . A crock pot would work fine
for this too .
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skippy
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Garage Chemist,
I was inspired by your idea of getting rich off of free amalgam scrap. So I spent a few hours running around the local dental centres trying to get
amalgam residues.
Unfortunately the climate doesn't seem terribly favorable to this endeavor in Canada. The dentists must have separators that clean the amalgam dust
and sludge from the water suctioned from the mouths of the patients - the separators are serviced every
couple of months and at that time the service company usually take the small bits and pieces of amalgam scrap too.
Thus the quantities that the dentists had were pretty minor - and thats when they were prepared to me have any at all! I gather that there are
guidelines to disposal that have been developed. When refused the amalgam at one place I smiled and said (all innocently) that it was funny that the
the same stuff they put in *peoples mouths* every day wasn't supposed to be given to anyone but their waste disposal company. She experienced what
was either embarrassment or cognitive dissonance, I can't say.
I can't blame the dentists who refused. Their caution is just a natural response to our culture of bureaucracy, litigation, etc.
Anyway, I collected almost a pound of amalgam scrap in about 6 hours. I got most of it later in the day when my game was getting better - instead of
just asking for the amalgam I made up an elaborate lie about what I was doing with it. I claimed I was making a large tooth/jaw themed sculpture and
was setting the polished scrap into giant resin jaws and teeth. One dentist thought it was a really neat idea, and he gave me about a third of my
take for the day. The idea kind of grew on me too as I repeated it - I started to believe it myself! I don't know if its the best lie to use
though, as I don't know if dentists really appreciate art. Anybody here got an idea for a yarn more tailored to dentist psychology?
In spite of my disapointing haul, I got lots of exercise and got to chat with some pretty dental hygenists, which made it less frusterating than it
might have been otherwise. Maybe with some practice I could double my take, but its no route to easy money, at least not in Canada.
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