IMPROVED METHOD FOR THE SEPARATION OF LEAD FROM PRECIOUS METALS
Year: 1884

page_text: I EDWARD HUBBARD RUSSELL, of Park City in the County of Summit and
Territory of Utah in the United States of America, Gentleman, do hereby declare
the nature of my Invention for an "IMPROVED METHOD FOR THE SEPARATION
OF LEAD FROM PRECIOUS METALS," and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
The object of this Invention is to secure the separation of precious metals and
lead from ores and metallurgical products and to effect the separation of the lead
from the precious metals.
To this end the Invention consists in the process as hereinafter set forth and
more specifically pointed out in the claim.
In the ordinary process of leaching or separating metals from ores by chemical
solutions the compounds of silver and gold are extracted by being dissolved out
with a solution of a hyposulphite of an alkali or alkali earth in which these
compounds are soluble.
The sulphate and chloride of lead however are often also present in the ores and
are likewise soluble in the hyposulphite solution. These lead compounds being
dissolved out of the ore or product along with the precious metals contaminate
the bullion which is produced. Owing to their presence in the bullion the
subsequent refining of that bullion becomes an expensive process, and the leaching
process has therefore been disadvantageous in the case of certain kinds of ores.
By my process this objectionable feature of the leaching method of treating ores,
is removed and the separation of the lead, from the precious metals is secured.
In the leaching process heretofore in use the byposulphite solution after it has
passed through the mass of ore and has dissolved out both the precious metals
and lead compounds is conducted into precipitating tanks and both the precious
and base metals are precipitated therefrom together usually as sulphides by means
of sodium or calcium sulphide.
•
In the carrying out of my improved process the solution after leaving the ore
is conducted into suitable precipitating tanks and a soluble carbonate is introduced
into or added to the solution in a sufficient quantity to convert all the lead
compound into carbonate of lead which is insoluble in the hyposulphite solution
and sinks to the bottom. It is best to add a slight excess of carbonate.

page_text: The soluble carbonate may be a carbonate or bi-carbonato of either sodium or
potassium but as a cheap article is very desirable, I prefer to use soda-aslı an
impure but inexpensive carbonate of soda.
I do not however limit myself to the use of soda-ash.
The compounds of the precious metals also contained in the solution after use
upon the ore or product are not precipitated with the lead by the carbonate.
After the precipitation of the lead the solution containing the precious metals is
conducted into tanks and these inetals are then precipitated by the common and
well known method usually as sulphides.
As a result of the use of my process the bullion produced from these sulphides
contains no lead but the lead is obtained by itself in such a form that it is of
considerable value.
This process then is far more economical for use in treating certain ores than
processes now in use. 1 find that copper if present in the solution will not be
precipitated with the lead but remains in the solution with the precious metals.
The action of the soluble carbonate when added to the hyposulphite solution
containing the precious metals and lead together is peculiar.
When added to aqueous solutions of the compounds of these metals as has
heretofore been done it precipitates lead aud precious metals all together.
But I have discovered that when added to the hyposulphite solution after
leaching therewith, the carbonate precipitates the lead alone and leaves the silver
gold and copper that are present in the solution unprecipitated.
This peculiar action of the carbonate when added to a hyposulphite solution
containing precious and base metals together, has I believe never heretofore been
known or made use of in quantitative or qualitative analysis in the laboratory nor
is it to be found set forth or described in any work on chemistry, or the treatment
of ores or metallurgical products.
My process is intended to be used particularly upon ores or products which have
been previously subjected to a chloridizing roast but is also applicable to some
raw ores in which the precious metals exist in forms which are soluble in the
byposulphito solution and to ores which have been exposed to chlorine gas or to
an oxydizing roast.
It is obvious that instead of leaching the ores or products with the hyposulphito
solution they can be subjected to the solvent action of the solution by any other
of the ways well known to those familiar with the art without departing from tho
spirit of my Invention.
I expect to apply my Invention to ores that have been subjected to an oxydizing
roast thus avoiding the use of 5 to 20% of salt which is required in the chloridizing
roasting. This is a very important point.
Having now particularly described and ascertained the maturo of my said
Invention and in what manner the same is to be performed I declare that what
I claim is :-
The improved method of separating lead from precious metal, consisting in the
preparation of a hyposulphite solution of the commingled metals and the treatment
of said solution with a soluble carbonate, substantially as hereinabove set forth.
Dated this 21st day of January 1884.