IMPROVEMENTS IN TREATING MIXED SOLUTIONS OF CHLORIDE OF COPPER AND SULPHATE OF SODA
Year: 1882

page_text: "
LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of IMPROVEMENTS IN TREATING MIXED
SOLUTIONS OF CHLORIDE OF COPPER AND SULPHATE OF SODA "
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the
Office of the Commissioners of Patents on the 25th November 1882.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, IMPROVE-
MENTS IN TREATING MIXED SOLUTIONS OF CHLORIDE OF COPPER AND SULPHATE
OF SODA,
This invention relates to the extraction of copper by what is known as the wet.
way, and consists in a method of treating solutions containing chiefly chloride
of copper and sulphate of soda.
So far as the wet method of extracting copper is pursued in this country, it is
applied chiefly to the extraction of copper from the residue left after sulphur for
the manufacture of sulphuric acid has been burnt off from cupreous pyrites. This
residue, known as pyrites cinders, or burnt ore, after being finely ground is mixed
with common salt and furnaced with free access of air. The sulphide of copper
contained in the burnt ore is thereby converted into sulphate, and the sulphate of
copper thus formed reacts upon the common salt present, with production of
sodium sulphate and copper chloride. These two bodies are then dissolved out
of the furnace product by water, and from the resulting mixed solution of chloride
of copper and sulphate of soda impure metallic copper is then precipitated by means
of metallic iron.
The present invention consists in first so treating the mixed solution of sodium
sulphate and copper chloride as to render it in a condition in which its copper can
be precipitated as oxide, and in then precipitating its copper as oxide by means of
lime or magnesia or a mixture of both lime and magnesia.
"
For all purposes for which the " copper precipitate produced by copper
extractors in this country is employed, oxide of copper would be equally available,
and for some of the purposes for which "precipitate" is at present employed, oxide
of copper would be preferable; while the cost of precipitating copper as oxide by

page_text: means of lime would be only from one-sixth to one-twelfth of the present cost of
precipitating it by means of metallic iron. But copper could not be precipitated
as oxide by means of lime from a mixed solution of chloride of copper and sulphate
of soda without precipitating at the same time an immense quantity of sulphate of
calcium, due to the presence of the sulphate of soda with the chloride of copper,
and so much sulphate of lime with the oxide of copper would render the latter of
very little value. Therefore under my present invention I first add to the copper-
extractor's mixed solution of chloride of copper and sulphate of soda a quantity of
chloride of calcium (which is a waste-product in the neighbourhood of most copper
extracting works) sufficient to decompose the sulphate of soda therein, and I
thus obtain a precipitate of sulphate of lime and a mixed solution of chloride of
copper and chloride of sodium. I separate the precipitate from the said mixed
solution, and wash the former, by any convenient means, and I then precipitate
the copper of the filtrate and that of the wash-waters by treating the filtrate and
wash-waters with lime, as milk or otherwise. Instead of lime magnesia may be
used for this purpose, or a mixture of lime and magnesia.
My invention thus consists in precipitating by means of lime or magnesia or a
mixture of both oxide of copper from mixed solutions of chloride of copper and
chloride of sodium obtained by treating.by chloride of calcium mixed solutions of
chloride of copper and sulphate of soda. My invention also includes the utilization
of the waste chloride of calcium produced in what is known as the Weldon process,
and of the waste chloride of calcium produced in the manufacture of chlorate of
potash, for treating mixed solutions of chloride of copper and sulphate of soda so
as to prepare them for the precipitation of their copper by means of lime or magnesia
or a mixture of both as above set forth,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Walter Weldon in the Great Seal Patent Office on the 23rd May
1883.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, " IMPROVE-
MENTS IN TREATING MIXED SOLUTIONS OF CHLORIDE OF COPPER AND SULPHATE
OF SODA,"
This invention relates to the extraction of copper by what is known as the wet
way, and consists in a method of treating solutions containing chicfly chloride of
copper and sulphate of soda.
So far as the wet method of extracting copper is pursued in this country, it is
applied chiefly to the extraction of copper from the residue left after sulphur for
the manufacture of sulphuric acid has been burnt off from cupreous pyrites. This
residue, known as pyrites cinders, or burnt ore, after being finely ground is mixed
with common salt and furnaced with free access of air. The sulphide of copper
contained in the burnt ore is thereby converted into sulphate, and the sulphate of
copper thus formed reacts upon the common salt present, with production of sodium
sulphate and copper chloride. These two bodies are then dissolved out of the
furnace product by water, and from the resulting mixed solution of chloride of
copper and sulphate of soda impure metallic copper is then precipitated by means
of metallic iron.
The present invention consists in first treating the said mixed solution of sodium
sulphate and copper for the separation of the sulphuric acid of its sodium sulphate,
and in then precipitating its copper either by lime or by a mixture of lime and
magnesia.
For all purposes for which the " 'copper precipitate" produced by copper
extractors in this country is employed, oxido of copper would be equally available,
and for some of the purposes for which "precipitate" is at present employed, oxide
of copper would be preferable; while the cost of precipitating copper as oxide by
means of lime or magnesia would be very much less than the present cost of
precipitation it by means of metallic iron. But copper could not be precipitated
as oxide by means of lime from a mixed solution of copper chloride and sodium
sulphate without precipitating at the same time an immense quantity of calcium
sulphate, due to the reaction of some of the lime on the sodium sulphate of the said
mixed solution; and so much calcium sulphate with the oxide of copper would
render the latter of very little value. Therefore, under my present invention I first
add to the copper extractors' mixed solution of copper chloride and sodium
sulphate, preferably, but not necessarily, after that mixed solution has been treated
for the separation from it of silver and gold, a quantity of calcium chloride
sufficient to decompose the sodium sulphate therein, and I thus obtain a precipitate
of calcium sulphate and a mixed solution of chloride of copper and chloride of
sodium. I separate the solid calcium sulphate from the said mixed solution of
copper and sodium chlorides in any convenient way, as will be well understood,
and having washed the said calcium sulphate by any convenient means, I then
precipitate the copper contained in solution as chloride in the filtrate and the
wash-waters by treating both the filtrate and the wash-waters with lime, as milk
or otherwise. Instead of lime there may be used for this purpose a mixture of
lime and magnesia.
My invention thus consists in precipitating in the state of oxide, by means
either of lime alone or of a mixture of lime and magnesia, the copper contained in
mixed solutions of chloride of copper and chloride of sodium, which mixed solutions

page_text: have been obtained by precipitating by means of calcium chloride the sulphuric
acid of the sodium sulphate contained in mixed solutions of sodium sulphate and
chloride of copper.
In witness whereof I, the said Walter Weldon, have hereto set my hand and
seal this twenty-first day of May in the year of Our Lord One thousand
eight hundred and eighty-three.
WALTER WELDON (L.S.)