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Purifying scrap


#1

hi all

i was just reading todays ganoksin email and i got to the bench tips
survey part with the “small melting jobs” part, could someone
explain what sal ammoniac will do to silver scrap, it also says about
mixing it with charcoal 1:5, were can i buy this sal ammoniac and
then its mixed with the charcoal and you add it to the scrap how much
do you add before you melt the metal

any help would be great

regards
jason


#2
i was just reading todays ganoksin email and i got to the bench
tips survey part with the "small melting jobs" part, could someone
explain what sal ammoniac will do to silver scrap, it also says
about mixing it with charcoal 1:5, were can i buy this sal ammoniac
and then its mixed with the charcoal and you add it to the scrap
how much do you add before you melt the metal 

If you take care of keeping your scrap clean, you should have no
reason to use it. It is used as an agent to remove from melt
chemical compounds formed by another flux ingredients. You can think
of it as a cleaner which cleans after cleaners. Charcoal is added to
absorb noxious gases and by-products which are released in the
process. 1 to 1, or 1 to 2 proportion should be plenty. Increasing
amount of charcoal is not going to hurt, so extra can be used for
safety. Activated charcoal is more effective. The amount of sal
ammoniac to use, will depend on how much impurities scrap contained
before. That is why refines always assay the scrap before refining
it. Using too much may cause loss of precious metal. However, for a
small shop, this loss is mostly theoretical.

Leonid Surpin
www.studioarete.com


#3
i was just reading todays ganoksin email and i got to the bench
tips survey part with the "small melting jobs" part, could someone
explain what sal ammoniac will do to silver scrap 

The ammonium chloride reacts with baser metals to form metallic
chlorides, such as tin, zinc, or iron chloride, etc. These are
insoluable in the metal, so they slag off with the melting flux. The
ammonium chloride, by the way, doesn’t melt to a liquid flux, but
skitters around on the molten surface turning to noxious vapors, so
use it with good ventillation. The :“vapor” is of course, chlorine
gas, which is toxic, but which is also what is reacting with, and
helping remove, the contaminant metals. The charcoal powder you add
is a reducing agent to lessen oxygen absorbtion and oxides. The combo
essentially act as partial refining fluxes, a helpful effect when
remelting/reusing scrap metal. Note that with gold casting alloys,
this will remove, at least partially, the deoxidizing agent, zinc,
that is often intentionally added, so the refining flux is not always
what you will want to use in melting depending on the metal and use.

, it also says about mixing it with charcoal 1:5, were can i buy
this sal ammoniac 

Chemical supply houses. Sometimes found in tiny bottles to supply or
resupply hobby chemistry sets from hobby shops. The stuff is not
expensive. Sal ammoniac is an old/obsolete name. Ammonium Chloride is
the proper chemical name.

and then its mixed with the charcoal and you add it to the scrap
how much do you add before you melt the metal 

A pinch, once the metal is at least starting to melt. doesn’t take
much. I usually add it, if using it at all, after the metal is fully
molten, and I pour as soon as most of the flux has dissipated and the
surface of the molten metal has “cleared”.

Peter


#4
Chemical supply houses. Sometimes found in tiny bottles to supply
or resupply hobby chemistry sets from hobby shops. The stuff is not
expensive. Sal ammoniac is an old/obsolete name. Ammonium Chloride
is the proper chemical name. 

Stain Glass supply companies sell sal ammoniac for cleaning
soldering irons. It is a few dollars for a bar that looks like soap.

Melissa


#5

Sal ammoniac used to be a common item in what used to really be
"hardware" stores. Anyone who regularly does soldering with a copper
"iron" will probably know where to get it. A good source for crafts
people is suppliers of materials for stained glass work. If you want
the primary source for the blocks see:

http://www.johnsonmfg.com/temp/SalBlock.htm

Their catalog has lots of other interesting stuff.

It is a common ingredient in a liquid solution Self pickling
soldering fluxes such as Batterns flux.

For use in casting you would want to grind up some from a soldering
block.

Fumes will not be “nice”.

jesse


#6
i was just reading todays ganoksin email and i got to the bench
tips survey part with the "small melting jobs" part, could someone
explain what sal ammoniac will do to silver scrap, it also says
about mixing it with charcoal 1:5, were can i buy this sal ammoniac
and then its mixed with the charcoal and you add it to the scrap
how much do you add before you melt the metal 

As Peter noted you add the sal ammoniac to molten metal. But it will
probably not do you any good for “cleaning” silver. It’s use as a
"refining flux" is in trying to clean up gold alloys that have been
contaminated with base metals. It will help in removing copper, zinc,
lead and iron from the gold alloy. The charcoal helps to reduce
oxygen pickup and acts as a means of distributing the sal ammoniac
over the surface of the melt.

James Binnion
James Binnion Metal Arts


#7

I wrote the article about sal ammoniac, I use the term always as its
what is printed on the carton, so it can’t be that outdated! I get
the stuff in small-ish block cheapest from stained glass supply
houses as its mainly sold for tinning soldering irons and you can
buy enough to last a year for under 3 bucks. It absorbs humidity
though and you have to keep it airtight and don’t use a nmetal lidded
jhar as it will readily corrode. A plastic film cannister works great
or any vacuum lidded cannister of plastic or acrylic- thoug I don’t
like to use plastics or recommend them, since it’s not disposable
or inteneded to be disposed of I feel ok in saying use the stuff
however a better container would be a well fitted ground glass
stoppered hjar as for holding acids or pharmacological ingredients.

I like the 1:5 ratio of sal ammoniac (ammonium chloride/w sulphates)
to powdered charcoal as it gives the brightest ingot and remains the
most malleable.Any stronger and you get a really hard to work ingot
that is bright but needs constant anealling…RER


#8
It is a common ingredient in a liquid solution Self pickling
soldering fluxes such as Batterns flux. 

Jesse, are you SURE about that? I don’t know differently for sure,
but this would surprise me. Batterns is not known for giving off lots
of obviously noxious fumes, and Ammonium Chloride, on heating to the
temps Batterns is used at, breaks down releasing chlorine gas. Blue,
noxious, choking stuff noticable even in small amounts. I’d thought
Batterns was mostly based on Borax, boric acid, and perhaps some
neutral fluorides… It might well be, however, in the sorts of
liquid fluxes sold for tin/lead or similar low temperature solders,
such as TIX flux, or Staybrite flux. Again, I don’t know that, but
those lower temp fluxes is where I’d expect to find ammonium chloride
if it’s used at all in a soldering flux. Most of those fluxes are
already based on a chloride, usually zinc chloride solution, so a
different chloride would seem to be reasonable as an addition…

Peter


#9
Jesse, are you SURE about that? 

read the msds-- I will dig out a few and send them.

jesse


#10
Jesse, are you SURE about that? I don't know differently for sure,
but this would surprise me. Batterns is not known for giving off
lots of obviously noxious fumes, and Ammonium Chloride, on heating
to the temps Batterns is used at, breaks down releasing chlorine
gas. 

Yes ammonium chloride is in the “self pickling” fluxes along with
borax and boric acid and water. It is what provides the “self
pickling” part.

James Binnion
James Binnion Metal Arts


#11
Ammonium Chloride, on heating to the temps Batterns is used at,
breaks down releasing chlorine gas. 

Decomposition temperature 338 C (640.4 F)
NH4Cl = NH3 + HCl

To quote from a Yahoo article
(http://answers.yahoo.com/question/index?qid 080115173322AAKwde)

When you heat ammonium chloride crystals (I have a 1lb jar) on a
plate or dish, you'll notice a strange white smoke. This smoke
is ammonium chloride! This is what happens... 

NH4Cl --> NH3 (gas) + HCl (gas) 

Then when the vapors rise and cool down the reaction just goes
backwards, making a smoke of NH4Cl particles. 

NH4 in general does not exist as a neutral species, only as an
ion. The breakdown of ammonium chloride generates hydrochloric
acid, but NEVER chlorine.

Not that breathing HCL is any better.

A more authoritative source, the Canadian equivalent of OSHA:
http://www.intox.org/databank/documents/chemical/ammchl/cie7.htm

Odourless, colourless, slightly hygroscopic crystals or white,
granular powder. Will not burn. Can decompose at high
temperatures forming irritating and toxic ammonia and hydrogen
chloride gases. Practically non-toxic.

Al Balmer
Sun City, AZ


#12
Odourless, colourless, slightly hygroscopic crystals or white,
granular powder. Will not burn. Can decompose at high temperatures
forming irritating and toxic ammonia and hydrogen chloride gases.
Practically non-toxic. 

Thanks, Al, and Jim, and others, for clearing up my apparent
misconceptions about just how ammonium chloride works and where it’s
found in our fluxes.

Peter