group of chemicals known as halides is composed of the elements
fluorine, chlorine, bromine, and iodine. We will ignore fluorine
because it does not dissolve gold. The elements listed above are
in order of their molecular weights, density, cost, and
reactivity. Chlorine is the lightest, cheapest and least reactive
while iodine is heaviest, most expensive, and fastest reacting.
Iodine is classified as a rare element. There are no ores
containing iodine. It is obtained primarily from extracting
seaweed, hence, the high cost.
was the first commercial gold extracting agent. In the late 1800s
it was introduced on the market as " DuPont Mining Salts".
Although I have no direct proof, Im sure that this was
nothing more than sodium hypochlorite, the stuff that Clorox is
made from. It was used by taking ore and chlorine and agitating
them in a "Pachuca Tank" or rotating the mixture in
lead-lined barrels. This method fell into disfavor with the
discovery that cyanide extraction was cheaper and easier for the
untrained miner to use. The usefulness of various extraction
techniques for the production of gold is attested to by the fact
that at the present more than 80% of the worlds gold
production is obtained by chemical extraction.
recent years there has been a resurgence of interest in halide
extraction of gold. Partly because of a better understanding of
the process but mostly because of the bad rap that cyanide has
received at the hand of the do-gooders, zealots and ignorant
crusaders. I understand that there is at least one commercial
companyare selling a sort of "magic" proprietary
chemical that only they can provide at a cost that knocks my socks
off. Let me give you a truism about chemistry, MERLIN THE MAGICIAN
DIED. THERE AINT BEEN NO MAGIC SINCE!!! You can do the same
thing in your carport or out in the mountains. All you need is a
little information that average Joe Beerdrinker just doesnt
have ready access to. I am going to give you (I hope) all the
information you need to do it. So, stay with me.
will read through all this stuff which, I know, is more than you
ever wanted to know I think you will eventually agree that you
will have learned some principles that you can use to great
advantage. I really hate to see folks trying to follow a cookbook
recipe to the point that when something goes a little wrong it
wrecks everything. I'm going to try to give you enough information
so that if something unexpected happens you will be able to deal
with it rather than panic.
hate to try to explain the principle of oxidation/reduction or "redox"
because I have never been able to put it into words that anyone
can understand. But, we have to try to get at least a rudimentary
understanding of this or you will never really understand what is
going on in gold extraction or any form of metallurgy.
There are three ways to look at redox. Oxidation is:
- The addition of oxygen.
- The removal of hydrogen.
- The loss of an electron.
Now I know that doesnt mean much to you but it is
important. For example when you recover mercury from a solution of
nitric acid which you have used to clean some amalgamated gold you
usually simply hang a piece of copper or aluminum in the clear
solution and mercury plates out on the copper and drips to the
bottom of the vessel. In this case the copper is reducing the
mercury in mercuric nitrate to mercury metal and oxidizing the
nitrate to copper nitrate. When something is reduced something
also has to be oxidized, they are simply the opposite of each
other. This is how a battery works. In the case of metals, which
are cations, that is they carry positive charges, the pure metal
is the reduced form. That is, iron metal is the reduced form of
iron. The rust that is on it is its oxidized form because it
has combined with oxygen to make iron oxide. If you take iron
oxide and put some rust remover (reducing agent) on it you remove
the oxygen and reduce the metal back to pure iron. Now, halides
are not metals. In fact they are the opposite. They carry negative
charges and are anions. So, In their elemental form they are
oxidized. Just the reverse of metals.
all of this important to you? Because if you are going to use
these chemicals you must be able to use them. If you want to store
iodine, it is much better to store it in its reduced form so that
it wont evaporate. And, if you want to dissolve gold with
it, it must be in its elemental or oxidized form. To summarize,
you must be able to shift the iodine (or other halide) from its
oxidized to reduced form. Im going to tell you how to do it.
you want your halide in its elemental or oxidized form,
simply add a little Clorox bleach. If you add an excess, Iodine
will precipitate from the water solution and settle to the bottom
as pure elemental, blue, iodine. If you want to dissolve the
iodine, you must reduce it. This you can do by adding a little Red
Devil Lye dissolved in water. The blue iodine will begin to go in
solution so that the solution will first turn bright blue and upon
addition of more Lye it will become colorless as all of the
iodine is reduced to sodium iodide. Hey. Great! Now we know how to
convert/handle it. As my son tells me re computers, you can make
it do what you want it to do. Now you have control.
a couple of facts re iodine. Elemental (oxidized) iodine will not
dissolve in water. So if it wont dissolve, how are we going
to use it? It has another characteristic. It will dissolve in
solutions of sodium iodide. I didnt do it, it just works
that way. That fact gives us our way to dissolve gold. We will
pursue that a little later.
should say that there are differences in the way the halides
behave but they are very minor differences. For example, chlorine
and bromine will not precipitate from solution when oxidized. That
makes them a bit more difficult to handle and recover, as we will
see later. I am simply using iodine as my example.
|Recovery of the Gold
have our ore with a nice red-brown solution of iodine and,
hopefully, a whole bunch of dissolved gold in the solution. We cant
sell it that way. Got to get it out and make it look like gold.
First we have to get rid of all the material that we have been
extracting. This can be done in a number of ways but probably the
most Basement way is to filter it. Depending on the scale that you
are working you can use a coffee filter in a funnel or a piece of
canvas in a 20 ft dia tank. Anyway, filter it and try to get a
rather clear solution. Remember that the solution must still be
red-brown. If it isnt, you have left your gold behind in the
filter. This is why I insisted on your being able to oxidize or
reduce at will. KEEP IT RED-BROWN.
you have your red-brown solution free of material, now, you can
let it go colorless or make it go colorless by addition of the Lye
solution. Your gold will now slowly settle to the bottom as a
black powder. Or, you can filter the solution through a fine
filter to recover the gold.
we got a whole bunch of gold but if we lose that iodine we are
still going to be in the hole. Remember, at this point it dont
look like iodine but it is still there. By this time you probably
have a pretty good volume of liquid with the iodine in it. If its
more liquid than you want to deal with simply dump in an excess of
Clorox , let the iodine settle to the bottom, pour off most of the
water, add some Lye solution and you have your sodium iodide in a
concentrated solution which is the way you want to store it
anyway. Ready for another extraction.
course, no one is going to buy that black powder from you. "
Sure its gold, anyone can see that! Take it somewhere else"!
To make this stuff look like gold again simply smelt it. I assume
most of you know how to smelt. If not, please contact me.
guys, It aint brain surgery. You can do it as well as me.
Please let me know how it comes out or if you have problems.
|The other Two Halides
have talked almost entirely about iodine. 99% of what I said about
the use of iodine applies to both chlorine and bromine. The
significant differences are;
- The price as discussed previously.
- Solutions of chlorine are colorless so you cannot rely on the
color to tip you off as to the eH of the solution. With chlorine
you will have to use an eH indicator dye which will not be
readily available, or (would I leave you with that problem?),
you can use your nose instead of your eyes. You will have to add
oxidizer to maintain a little chlorine smell coming off the
- So, what oxidizer do I use? Same as with iodine. You use
chlorox. However, chlorox is very weak and you would have to use
great volumes of it to maintain some chlorine in solution. You
should use the stuff that chlorox is made of, sodium
hypochlorite. This is a solid, white powder which in a 5.0%
solution is chlorox. This chemical can be obtained at any
chemical supply. Now if you cant or wont go to that
effort there is still another alternative. You see, we never
leave you hanging without another way to skin the cat. Almost as
good as sodium hypochlorite is our old friend, swimming pool
chlorine. This is calcium hypochlorite. It works very well. It
just doesnt dissolve very well. Again, we never leave you
without a way to escape. Just add a little lye solution and it
will go right in. You have converted it to sodium hypochlorite.
Dont add too much, just enough to put it in solution.
- Remember chlorine is very slow. You will have to maintain
this system for several hours to a day or more.
- Like all of the halides, if you allow the solution to go
acid, the chlorine will rapidly boil off and if you are close by
will be extremely uncomfortable. Bromine and iodine are not so
bad. They are not nearly so volatile and will give you a little
more time to rectify the situation by addition of a little lye
- If you are extracting with halides, in particular, chlorine
where you have no visual reference as to what is happening, you
should have some hydrochloric (muriatic) or sulfuric acid at
hand. If your reaction should start to slow down and you are
sure you have an excess of halide in solution you might have to
add a little acid in order to liberate the halide from its
salt form in order to keep sufficient free halide to ensure a
good extraction. If you can keep the pH at say 8.5 you will be
- If chlorine production should get out of hand, you probably
should have some solution of sodium thiosulfate on hand. It can
be bought from any chemical supply. This is the stuff that
tropical fish freaks use to treat tap water to destroy chlorine.
You will need much more than they use however. This is a good
way to neutralize any solution you wish to dump. Your neighbors
will probably appreciate your thoughtfulness.
- Just a little about bromine. Its a bit expensive so we
are not going to throw it away, right? Bromine is rather nasty
stuff to handle in its elemental form. It is a liquid, which is
sold sealed in 1-LB glass ampoules. When you break the container
you have to use it or contain it some other way. It has a way of
fuming right through the tightest bottle-cap type seals. The
only way you might do it successfully is to seal around the cap
with hot paraffin. Lets dont do it that way. Always
an option, right? Since we are rather knowledgeable about
oxidation/reduction we can handle it in a more sophisticated
way. We can buy it in its reduced and cheaper form, sodium
bromide. After all, we know how to convert it to elemental
bromine; it just takes a little clorox, right? After all, thats
what we are going to store it as anyway. When Clorox is added
and the bromine oxidized to its active form, like iodine; it
exhibits a distinctive color, deep red. We are now a bit smarter
than the average bear
that we can jump around in redox reactions like a monkey in a fig
tree let me add just one final "consejo". Whatever you
decide to do with these extractions, please. Read the above
several times until you are certain that you understand it well
enough to control the reactions. Its not hard, use common
sense, and if thing start to go sour dont panic, fix it.