Improvements in Making White Pigments of Lead.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Making White Pigments of Lead.
I, JESSE GORDON, of Huntingdon Villa, Bridge of Allan, in the County of Stirling,.
North Britain, Metallurgist, 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, that is to say:-
My said Invention has for its object the making of white pigments of lead from
galena in an improved manner, whereby labor and fuel, are economised, and larger
and more uniform products are obtained than heretofore.
In carrying out my Invention I grind the galena into a fine powder by means of
mill stones or other suitable apparatus, and I project the powder by means of com-
pressed air or otherwise in one or more jets or streams into the upper part of a cupola
or other suitable furnace. By way of example I show a furnace such as I prefer
to employ upon an accompanying sheet of explanatory drawings, figure, 1, of which
is a vertical section, figure, 2, being a horizontal section.
The furnace is of a square form in plan, the lower part, A, of its interior being
somewhat narrower than the upper part, B, and the bottom, C, is of the kind known
as a brasque bottom, having at the front the usual tymp, D, and fore hearth plate E.
Heat is generated by means of coke supplied to the lower part, A, of the furnace
through a fuel door, F; and the necessary air is injected by means of tuyeres, G,
connected to a blast pipe, H.
In the example shown in the drawing the powdered galena is injected through a
single inlet, J, into the upper part, B, of the furnace, and it takes fire with
deflagration, producing heat and flame, the sulphide of lead of which the ore entirely
or mainly consists, becoming oxidised and converted into a white vapor or fume
which comprises sulphite, sulphate, and oxide of lead in variable proportions.
The
For feeding in the powdered galena in a continuous and regular manner, there is
provided a hopper, K, into which it is put, and from the bottom of which it is moved
by a rotating conveying screw, L, driven at a suitable rate in any convenient way,
along a horizontal duct, M, from which it drops down a conical pipe, N.
pipe, N, extends downwards through a spherical box, P, into which the compressed
air is led by a pipe, Q, the pipe, N, terminating a little below the box, P, in a
pipe, R, extending down to the inlet, J, in the top of the furnace. In the inlet, J,
a small cone is held to spread the stream of mixed air and galena; and the inlet
pipe, R, is prevented from becoming overheated by a water jacket, S, through which
a current of water is maintained.
The heat due to the coke in the furnace should be sufficient to cause the combustion
or deflagration of all or nearly all the powdered galena injected. Incombustible or
non-volatile impurities fall to the lower part of the furnace; and if there is copper
pyrites in the ore the copper separates and falls and can be economically recovered
from the furnace residues. Also, if any of the galena escapes combustion in the
upper part of the furnace it falls on the coke and becomes to a greater or less
extent smelted and volatilised.
The white fumes pass from the furnace, through a flue, T, being drawn by means
of suitable exhausting apparatus, and are passed into a wet fume condenser which is
by preference of the kind described in the Specification of Patent No. 5239 of 1878
granted to Andrew French and others. The water in the condenser is by preference
acidulated with hydrochloric acid to dissolve and thereby remove zinc, iron, alumina.
and silver, as in the process described in the Specification of Patent No. 5193 of 1883
granted to Andrew French. The pigment may be afterwards treated and finished as
described in the same Specification.

page_text: 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 improved process for making white pigments of lead in which galena in a
finely powdered condition is injected into the upper part of a furnace heated with
coke, the galena being oxidised and converted into a fume substantially as hereinbefore
described.
Datadethia Twants tourth day of June 1890
EDMUND HUNT,
Applicant's Agent.