Process and Apparatus for the Production of the Acetates of Lead, Copper, and the like..
Year: 1897

page_text: Date of Application, 19th Mar., 1897-Accepted, 5th June, 1897
COMPLETE SPECIFICATION.
Process and Apparatus for the Production of the Acetates of Lead,
Copper, and the like..
I, ADOLF SCHMIDT, Director of The Actien Gesellschaft für Treber-Trocknung,
of 49 Kölnische Strasse, Cassel, in the German Empire, 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,
reference being had to the accompanying drawings and to the letters and figures
marked thereon, that is to say :-
Heretofore, in the production of acetates of metals, the necessary oxidation of
such metals has been obtained either by exposing them in a moist state to the air,
or by beating them in the presence of acetic acid, to which a suitable quantity of
an oxidising substance has been added.
The first mentioned process is employed for producing sugar of lead, and
subacetate of copper known as German verdigris; while the second process is
adopted for producing neutral acctate of copper, wherein copper turnings or
chippings, or plates, are treated in the same manner as lead.
Both these processes have the serious disadvantage of being slow, as well as
occasioning considerable waste of acetic acid.
My invention obviates the above disadvantages, and it has for its object to
produce oxidation by the use of commercial oxygen gas, thereby greatly shortening
the duration of the process, as well as preventing waste of acetic acid.
In the production of sugar of lead, or of neutral acetate of copper, the metal is
exposed, in repeated succession, in suitable apparatus, to the action of oxygen, and
then to that of acetic acid, which latter absorbs the oxide formed, until complete
saturation.
If it be desired to produce dibasic acetate of copper, copper plates are exposed
in closed vessels to the simultaneous action of oxygen and the vapour of dilute
acetic acid until the required degree of oxidation and saturation is reached.
For the purpose of producing neutral acetate of lead, I employ apparatus such
as represented in Fig. 1, and in which:
A and A. are two hermetically closed cylindrical iron vessels, of equal size, each
consisting of two separate chambers or compartments a and b. The compartments a
are either plated with acid resisting material, or are enamelled, and are closed by a
cover c at top. The apparatus is provided with the usual fittings, such as steam
inlet valve h, safety valve (not shewn) pressure gauge e, inlet cock f, and draw off
cock g.
The vessel A' is provided with a pressure reducing valve k for supplying the
oxygen under pressure. The compartment 6 serves for heating the compartiment a,
by means of steam, which enters through the valve h and leaves through the pipe i,
to which latter is connected a condensed water ejector. The apparatus may,
however, be heated by any other suitable means.
The two chambers a, a, of the vessels A and A¹ are brought into communication
with each other by two pipes and u, the upper one 7 of which, with its valve d,
allows of the oxygen being passed alternately from one vessel to the other, while
the lower one.u, allows the liquid to pass from one vessel to the other, and is, for
this purpose, provided with a pump m.
i

page_text: The process is carried out in the following manner:
Both compartments a, a, are half filled, through their manholes c, c, with shot, or
small pieces of lead. The vessel A¹ is then supplied through the cock f with a 45
to 50% solution of acetic acid until the compartment a is about three quarters
filled.
The material in a is heated to about 50° to 60° C. by admitting steam into the
compartment b, and as soon as the vapours begin to be evolved and drive out the
air from the compartment, the manhole c is closed. The pump m is then started,
and pumps the acetic acid from the vessel A' into the vessel A, while, at the same
time, oxygen is introduced, from a steel cylinder, through the carefully regulated
pressure reducing valve k, into the vessel A¹. When nearly all the acetic acid has
been pumped from the vessel A' into the vessel A, and the air in the latter has
been driven out therefrom by the vapours of the acid, the manhole of this vessel is
closed, and the remaining acid is then pumped from the vessel A¹ by opening the
valves d, d.
The moist lead in A' is acted upon by the incoming oxygen and quickly becomes
oxidised.
In about an hour, the acetic acid is pumped back from the vessel A
into A. This acid being strongly agitated by the pumping action at once
vigorously attacks the oxide of lead while, at the same time, it drives out the
oxygen through the communicating pipe into the vessel A where it oxidises the
lead contained therein; it is then again allowed to stand for an hour. The acetic
acid is afterwards pumped once more from the vessel A¹ into the vessel A where it
absorbs the oxide of lead and drives the oxygen back into A'.
The process is continued until the acid is completely saturated with oxide of
lead. During the whole time of working, the temperature must be kept at 50° to
60° C. with a pressure of atmospheres oxygen. Tests are taken at frequent
intervals to ascertain the degree of saturation, and the supply of oxygen is shut
off as soon as saturation is complete.
The solution of sugar of lead is then drawn off, through the cock 9, for
final treatment, after which the vessel A¹ is charged with a fresh quantity of
acetic acid, filling it again to about three quarters, and heat is applied to raise
the temperature to between 50° and 60° C., and so on in the same manner as herein
above described.
The manufacture of neutral acetate of copper, by means of commercial oxygen,
is carried out in the same manner and in the same apparatus, the only difference
being that, in this instance, copper turnings or chippings, or old copper, is used
in place of the lead.
For manufacturing subacetate of copper, by the use of commercial oxygen,
it is necessary to modify both the process and the apparatus. A suitable apparatus
for this purpose is shewn in Fig. 2, and consists, as before, of a hermetically
closed cylindrical iron vessel forming two separate compartments a and c*, and an
intermediate compartment 6 which is in communication with the compartment a
through the perforated false bottom n. o is the manhole, e the pressure gauge,
the
pressure reducing valve for the oxygen under pressure, g the draw off
cock for the acetic acid, & the filling tap and funnel for introducing the acid,
and the heating chamber having a steam inlet h and a steam outlet i.
The process is carried out in the following manner:
P
Copper plates of about 5 m in thickness are piled in the compartment a, room
being left for a man to stand in the middle, and spaces are left between the
plates of about 10 to 15 m/m by placing wooden lathes between them. The
compartment being thus filled, the acetic acid is introduced through the funnel,
and as soon as the level of the acid reaches the narrow end of said funnel, the
cock k is closed. The acid used should be either wood vinegar, or a weak solution
of acetic acid. The temperature is then raised by admitting steam to the com-
partment and is kept constant at about 50°. The vapours of the acid pass
through the holes in the false bottom n into the compartment a where they come
freely into contact with the copper. When all the air has been driven out, and the

page_text: vapours of the acetic acid begin to escape, the manhole must be closed, and the
pressure reducing valve p opened to introduce the oxygen, which latter, together
with the weak acetous vapours, acts on the copper. By regulating the relative
quantities of oxygen and acid, so as to have either an excess of oxygen, or of acid,
it will be easy to produce a salt of any basicity.
On it being found that the copper plates are covered with a sufficiently thick
coat of oxide, they are removed from the vessel and the verdigris scraped off them,
after which they are returned to the vessel. When the plates become too thin and
weak, they are replaced by fresh ones, the old ones being used up completely in
the manufacture of neutral acetate of copper by the first process.
The verdigris which has been scraped off the plates is collected, pressed in forms
or moulds, and dried, when it is ready for use.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same may be performed, I declare that I
claim:
.
1. The process for producing the acetates of lead, copper, or the like, consisting
in treating the metals with commercial oxygen and acetic acid under pressure, and
accompanied by heat, substantially as set forth.
2. The apparatus for carrying out the herein described process for producing
neutral acetates, consisting of two receiving vessels for the metals, in which the
oxidation and the absorption of the oxide are produced alternately, and in which
apparatus the acetic acid solution is pumped alternately from one vessel into the
other, while the oxygen is driven through a separate communicating pipe,
substantially as described with reference to Fig. 1 of the drawings.
3. The modified apparatus for use in connection with the. herein described
manufacture of acetate of copper of any desired basicity, consisting of a
vessel divided by a perforated false bottom into two compartments, in the lower
of which the acetic acid is vapourized, while in the upper the copper is exposed
to the action of oxygen and the vapours of the acid, substantially as described
and shewn with reference to Fig. 2 of the drawings.
Dated this 19th day of March 1991.
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, and 5ª, Market Street, Nottingham,
Agent for the Applicant.