Gold Extracting Reagents.
Year: 1891

page_text: Date of Application, 24:h Jan., 1891
Complete Specification Left, 23rd Oct., 1891-Accepted 16th Jan., 1892
PROVISIONAL OF ECIFICATION.
Improved Gold Extracting Reagents.
I, JAMES HOLMS POLLOK, B. Sc. late Assistant to the Professor of Chemistry
in the University of Glasgow, and now Consulting Chemist, 27 St. Vincent Place
Glasgow aforesaid do hereby declare the nature of this invention to be as
follows:-
My invention relates to the method of extracting gold by chlorination, and
preferably by chlorination under hydraulic pressure. It has for its object to reduce
the weight of chemicals used, and make them more efficacious, thus saving freight,
and extracting a larger proportion of gold. Whereas I formerly used nitre cake
or bisulphate of soda as explained in my Patents Nos. 17495, A.D. 1887, 16796,
A.D. 1888, 5578, A.D. 1889, and 10298, A.D. 1889, I now melt the nitre cake
down with a certain small proportion of sulphite of soda, and if it is desired to
increase the proportion of acid in the nitre cake I melt it down with sulphuric acid,
adding the sulphite of soda after the acid. The addition of sulphite of soda has
the effect of destroying or removing any small traces of nitric acid present in the
cake, and it is found that traces of nitric acid have a detrimental effect in
preventing the precipitation of a certain proportion of the gold on the subsequent
addition of ferrous sulphate. As this foss in precipitation is sometimes as much
as 2 and 3% of the whole gold present, the value of using the reagent as prepared
above is obvious, for it enables the whole of the gold extracted to be precipitated
and recovered by the subsequent operations.
Whereas I also formerly used crystallized ferrous sulphate or ordinary copperas
to precipitate the gold extracted, I now detydrate or partially detydrate the ferrous
sulphate which detydrated ferrous sulphate is easily packed in iron drums and will do
more work for a given weight, consequently saving in freight and carriage.
Preferably I detydrate the ferrous sulphate until it has but one atom of water in
the molecule, and this I do by breaking up the green vitrial or copperas so that it
will pass through a screen with inch meshes, and then placing the broken crystals
in an iron or steel vessel surrounded and heated with steam under pressure and
so adjusted that I can regulate the temperature of the vessel. I have further
a mechanical stirring or agitating apparatus whereby the ferrous sulphate is
continually stirred about. I commence the detydration at 100° Centigrade. and
gradually rise the temperature as the operation proceeds, finishing at a temperature
of about 150° Centigrade. By this means I get a salt having the formule FeṢoч
HO. There is practically no oxidation of the salt, it keeps well when packed
in air-tight iron drums, and dissolves readily in water, the solution being a most
efficient precipitant for gold extracted by chlorine.
Dated this 23rd day of January 1891
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.
COMPLETE SPECIFICATION.
Improved Gold Extracting Reagents.
I, JAMES HOLMS POLLOK, B. Sc. late Assistant to the Professor of Chemistry
in the University of Glasgow, and now Consulting Chemist, 27 St. Vincent Place,
Glasgow aforesaid do hereby declare the nature of this invention and in what
017

page_text: manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
My invention relates to the method of extracting gold by chlorination and
preferably by chlorination under hydraulic pressure. It has for its object to reduce
the weight of chemicals used and make them more efficacious thus saving freight,
and extracting a larger proportion of gold. Whereas I formerly used nitre cake
or bisulphate of soda as explained in my Patents Nos. 17495 A.D. 1887, 16796,
A.D. 1888, 5578, A.D. 1889, and 10298 A.D. 1889, I now melt the nitre cake
down with a certain small proportion of sulphite of soda, and if it is desired to
increase the proportion of acid in the nitre cake I melt it down with sulphuric
acid, adding the sulphite of soda after the acid. The addition of sulphite of soda
has the effect of destroying or removing any small traces of nitric acid present in
the cake, and it is found that traces of nitric acid have a detrimental effect in
preventing the precipitation of a certain proportion of the gold on the subsequent
addition of ferrous sulphate. As this loss in precipitation is sometimes as much as
2 and 3% of the whole gold present, the value of using the reagent as prepared
above is obvious, for it enables the whole of the gold extracted to be precipitated
and recovered by the subsequent operations.
Whereas I also formerly used crystallized ferrous sulphate or ordinary copperas
to precipitate the gold extracted, I now detydrate or partially detydrate the
ferrous sulphate, which detydrated ferrous sulphate is easily packed in iron drums,
and will do more work for a given weight, consequently saving in freight and
carriage. Preferably I detydrate the ferrous sulphate until it has but one atom of
water in the molecule, and this I do by breaking up the green vitriol or copperas
so that it will pass through a screen with inch meshes, and then placing the
broken crystals in an iron or steel vessel surrounded and heated with steam under
pressure and so adjusted that I can regulate the temperature of the vessel. I have
further a mechanical stirring or agitating apparatus as shown in the annexed
drawing whereby the ferrous sulphate is continually stirred about. I commence
the detydration at 100° Centigrade, and gradually rise the temperature as the
operation proceeds, finishing at a temperature of about 150° Centigrade. By this
means I get a salt having the formula FeSo, H.O. There is practically no
oxidation of the salt, it keeps well when packed in air-tight iron drums, and
dissolves readily in water, the solution being a most efficient precipitant for gold
extracted by chlorine.
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 :-
1. The improved gold extracting reagents substantially as and for the purposes
herein before described.
2. In chlorination, the use of nitric cake melted with sulphuric acid and sulphite
of soda and detydrated ferrous sulphate, substantially as described.
Dated this 22nd day of October 1891.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.