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Salts for cleaning scrap gold


#1

I’ve heard of salts that can be added to used gold to help clean out
the impurities when melting. Does anyone know what these salts are
and where they can be purchased?

Jim
Lake Worth, FL.
www.enamelart.com


#2
 heard of salts that can be added to used gold to help clean out
the impurities when melting. Does anyone know what these salts are
and where they can be purchased? 

The most commonly used salts are our familier fluxing salts, Borax
and boric acid. A melting flux of the two mixed together will be
good for removing a significant portion of oxide impurities. It’s a
good starting point for a standard melting/casting flux. A little
charcoal powder added to it will improve the oxide removal ability as
well. But these only reduce/remove oxides, they’re not true refining
fluxes.

Of those, one commonly useful one is ammonium chloride. Get it from
any science supplier, or the area of the hobby shop where they sell
refill chemicals for the toy chemistry sets… Also known, old style
terminology, as sal ammoniac. A little added to a melt will tend to
form metalic chlorides with more reactive metals such as iron, zinc,
tin, lead, etc. Since the chlorides of these metals aren’t soluable
in the melt, they then slag off, mixing with your normal melting
flux. Use only with good ventilation, as you evolve a bunch of
noxious blueish fumes, including chlorine gas, I think, when you use
this. It doesn’t melt like borax/boric acid flux when applied, but
the dry powder skitters around on the surface of the molten metal as
it sublimes directly to a gaseous state. Iron and zinc in
particular, can be reduced this way. Note that for casting alloys,
this also means your deoxidizers, or at least some of them, are
being removed too. So use this for scrap you’re attempting to
reclaim for fabrication purposes, not for metal intended for decent
castings. Note too, that these can improve contaminated metal, but
it’s not a substitute for actually refining scrap metal. It reduces,
but doesn’t completely eliminate, the contaminants.

to a certain extent, though much less active in this regard, common
table salt will do some of the same thing. Not as active though.

In both cases, the net effect is to toughen the gold, as the
impurities removed are often responsible for metal that tends to
crack and fail during rolling. they’re both most effective on higher
karats.

Peter Rowe


#3

Dear Jim, I’ve always used table salt. Right from the shaker. Best
Regards, Todd Hawkinson TR the Teacher


#4

Hello Jim

This salt is called auropurifax

To purchase at the Netherlands it is available at “Bijou Moderne” in
Bleiswijk tel +31 10 5296600 Fax +31 10 5290088 Mail
info@bijou-moderne.nl The Dutch price is approx. =80 9.- for 45 gram

It is also available in Germany at Karl Fischer GmbH Pforzheim tel:
+46 7231 31 0 31 Fax: +46 7231 31 0 300 Mail info@fischer-phorzheim.de
And : www.fischer-phorzheim.de

some old text to come with it

Auropurifax is gold cleaning powder, It absorbs the wrong alloys and
removes dirt. First you have to remove the steel particles with a
magnet then if you are not shore you have everything, boil your gold
in sulphuric acid. You melt your gold sjit with (depending on the
amount of dirt) some Auropurifax (2 - 10 weight %), stir good and you
get a wonderful ductile alloy back, which does crack during rolling.
You can even clean teeth gold with this stuff.

Greetings

Martin Niemeijer


#5

Hi Jim, The mixture (Filux) is available from Twain Manufacturers
(Pty) Ltd. See: www.maxpages.com/twainwax Regards, Ed.


#6

Hi Jim, Traditionally, a pinch of saltpeter (sodium nitrate) is added
to the melt to eliminate impurities. You can get this at any
chemical supplier.

John