A Process for Freeing Copper from Arsenic.
Year: 1893

page_text: Date of Application, 27th Feb., 1893-Accepted, 22nd Apr., 1893
COMPLETE SPECIFICATION.
A Process for Freeing Copper from Arsenic.
FRED BEDDOW STONE Analytical Chemist Eardley Villa. Picardy Hill
Belvedere Kent, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
I melt copper in a reverberatory or other furnace suitable for melting and oxidising
copper. And free it from iron lead and zinc, in the usual manner carried out in
copper smelting works, if that has not already been done.
I then allow the copper
to remain in the furnace so as to become oxidised to such an extent, as to render it
brittle and cause it to present a dull red fracture when broken. And when it
oxidised to the above extent I add (preferably in small quantities at a time) to the
molten copper, if it contains one or more per cent. of arsenic, an amount of sodium
carbonate (dried or anhydrous by preference) or sodium hydrate, or potassium
carbonate, or potassium hydrate or sodium nitrate, or potassium nitrate, equivalent
to ten times the weight of the arsenic contained in the copper.
And I keep the copper and the sodium carbonate or any of the other said
chemicals, in a molten state from 20 to 30 minutes.
The molten copper is
afterwards allowed to run from the furnace in the usual manner, and is cast into
bars or "pigs." When it is again melted and refined or "poled in the usual
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manner for the production of tough copper. Or the copper may be refined or
poled" immediately after it has been allowed to run from the furnace.
When tapping the furnace I am careful not to allow the slag, produced from the
sodium carbonate or any of the other said chemicals, to run with the copper as the
arsenic (contained in the slag) or a portion of it would in that case be reduced to
metal in the subsequent refining process and so contaminate the copper.
I find the above proportion of sodium carbonate or any of the other said
chemicals, amply sufficient if the temperature is sufficiently high to maintain the
copper in a molten state; and the surface of the copper is at the same time kept
well covered with the sodium carbonate or any of the other said chemicals. But if
from any cause such as above mentioned, the operation has not succeeded in
removing the arsenic the first time, the copper is again melted and the operation
repeated.
When the copper contains less than one per cent. of arsenic, I add the same
quantity of sodium carbonate or any of the other said chemicals as would be
required for copper containing one per cent. of arsenic, and carry out the process in
the manner before mentioned. But I do not confine myself to the above mentioned
proportions of sodium carbonate or any of the other said chemicals, nor to the
above mentioned period during which the same are allowed to act.
The result is that the copper is either freed absolutely from arsenic, or only
minute traces remain.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is-
The addition of sodium carbonate or any of the before mentioned chemicals to
the molten copper as above stated, when it has reached the particular stage of
oxidation previously referred to.