IMPROVEMENTS IN PROTECTING CD SURFACE OF MIRRORS AND OTHER ARTICLES OR GLASS"
Year: 1858

page_text: LETTERS PATENT to Justus Baron Von Liebig, of Munich, in the
Kingdom of Bavaria, for the Invention of "IMPROVEMENTS IN PROTECTING
CD SURFACE OF MIRRORS AND OTHER ARTICLES OR GLASS"
PROVISIONAL SPECIFICATION left by the said Justus Baron Von Liebig
at the Office of the Commissioners of Patents, with his Petition, on the
3rd June 1858.
I, JUSTUS Baron VON LIEBIG, of Munich, in the Kingdom of Bavaria, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN PRO-
TECTING THE SILVERED SURFACE OF MIRRORS AND OTHER ARTICLES OF GLASS," to be
as follows
My Invention consists in protecting the silvered surface of mirrors and
other articles of glass, by depositing thereon.a coating of copper or gold, or.
other meial, by the agency of electricity combined with the use of a neutral,
solution of the double salt tartrate of oxide.of copper and soda (potash or
ammonia), or an alkaline solution of gold, nickel, or other metals, which may
be prepared as herein-after described.
...
The protecting coating may be obtained in the following manner :,A glass,,
plate, of which one surface has already been covered by a reflecting film, of.,
silver by any of the known processes for that purpose, is placed horizontally.or
vertically in a tub or vessel, which may, be composed of gutta percha or off

page_text: wood, lined with caoutchouc or of other suitable material, and in the same tub
at the distance of about half an inch from the silvered surface of the glass
plate, a sheet of copper of the same dimensions as the glass plate is also fixed.
The tub is now filled with the herein-after described solution of the said salt
of copper, nickel, or gold, and the silver coating of the glass plate is brough
in contact, by means of a metallic wire or conductor, with the negative pole or
zinc end of a voltaic battery, while the sheet of copper is brought in contact
with the positive pole or copper end of the same voltaic battery. A battery,
such as that of Bunsen, consisting of one voltaic couple only, may be employed
with advantage. The silver filmouthcglass plate becomes covered immediately
by a coating of copper; but to give sufficient thick ness to this coating the glass
plate is allowed to remain in the solution from ten to twenty-five minutes,
This mode may be applied for the coating of other surfaces besides planc
surfaces with exactly the same effect. The silver surface of the mirror is
protected by the coating of copper thus applied from the tarnishing action of
the sulphuretted hydrogen in the air, and also from injury by mechanical
abrasion.
In the process described, an alkaline solution of a salt of gold or nickel
may be substituted for the solution of copper with the same effect.
The neutral solution of copper used is prepared by dissolving twenty-five
(25) parts of sulphate of copper in one hundred parts of water, adding a
solution of twenty-eight (28) parts of the double tartrate of soda and potash
(commonly, called Rochelle salt) in the same quantity of water, which is
sufficient to precipitate the oxide of copper in the form of tartrate, and after-
wards adding caustic soda, potash, or ammonia, in such proportion as to re-
dissolve the precipitate. To one volume of this solution, which ought to be
perfectly neutral, is added an equal volume of water. The alkaline gold
solution is prepared by dissolving one part of the double chloride of gold and
sodium in one hundred and twenty parts of water, and adding to that solution
two parts of caustic soda. The alkaline solution of nickel is prepared by
adding a slight excess of ammonia to a solution of one part of sulphate of
nickel in (40) forty parts of water.
I am aware that various plans have been proposed for protecting the
silvered surface of looking-glasses as, for example, by the application of a coat
or coats of varnish or paint, or by depositing thereon metallic coatings by the
ordinary electrotype processes; but these plans, including the use of the
common salts of copper, which possess an acid reaction or cyanurets, cannot
be practically employed with advantage. I do not, therefore, claim their use,
but what I claim is the use of the double tartrate of oxide of copper and

page_text: soda, potash or ammonia, in the electro-plating process, and the mode of
protecting silvered surfaces of glass by the agency of electricity, in combination
with a neutral solution of copper and the alkaline solution of inctals, as
herein described.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Justus Baron Von Liebig in the Great Seal Patent Office on
the 25th November 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JUSTUS
Baron VON LIEBIG, of Munich, in the Kingdom of Bavaria, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of June, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Justus Baron Von Liebig, Her special licence that I, the said Justus Baron
Von Liebig, my executors, administrators, and assigns, or such others as I,
the said Justus Baron Von Liebig, my executors, administrators, and assigns.
should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for "IM.
PROVEMENTS IN PROTECTING THE SILVERED SURFACE OF MIRRORS AND OTHER ARTICLES
OF GLASS," upon the condition (amongst others) that 1, the said Justus Baron
Von Liebig, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what manner
the same was to he performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately after the
date of the said Letters Patent.
NOW KNOW YE, that I, the said Justus Baron Von Liebig, do hereby
declare the nature of my said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement :-
My Invention consists in protecting the silvered surface of mirrors and
other articles of glass, by depositing thereon a coating of copper or gold, or
other metal by the agency of electricity, combined with the use of a neutral.
solution of the double salt tartrate of oxide of copper and soda (potash or

page_text: ammonia), or an alkaline solution of gold, nickel, or other metals, which may
be prepared as herein-after described.
The protecting coating may be obtained in the following manner:-A glass
plate, of which one surface has already been covered by a reflecting film of
silver by any of the known processes for that purpose, is placed horizontally or
vertically in a tub or vessel, which may be composed of gutta percha or of
wood lined with caoutchouc or of other suitable material, and in the same tub,
at the distance of about half an inch from the silvered surface of the glass
plate, a sheet of copper of the same dimensions as the glass plate is also fixed.
The tub is now filled with the herein-after described solution of the said salt
of copper, nickel, or gold, and the silver coating of the glass plate is brought
in contact by means of a metallic wire or conductor with the negative pole or
zinc end of a voltaic battery, while the sheet of copper is brought in contact
with the positive pole or copper end of the same voltaic battery. A battery,
such as that of Bunsen, consisting of one or more voltaic couples, according to
the dimension of the plate to be coppered, may be employed with advantage.
The silver film on the glass plate becomes immediately covered by a coating
of copper, but to give suflicient thickness to this coating the glass plate is
allowed to remain in the solution from ten to twenty-five minutes. This mode
may be applied for the coating or other surfaces besides plane surfaces with
exactly the same effect. The silver surface of the mirror is protected by the
coating of copper thus applied from the tarnishing action of the sulphuretted
hydrogen in the air, and also from injury by mechanical abrasion.
In the process described, an alkaline solution ofa salt of gold, or nickel, or
tin, may be substituted for the solution of copper with the same effect.
The neutral solution of copper used is prepared by dissolving twenty-five
(25) parts of sulphate of copper in one hundred parts of water, adding a
solution of twenty-eight (28) parts of the double tartrate of soda and potash
(commonly called Rochelle salt) in the same quantity of water, which is
sufficient to precipitate the oxide of copper in the form of tartrate, and after-
wards adding caustic soda, potash, or ammonia, in such proportion as to
re-dissolve the precipitate. To oue volume of this solution, which ought to be
perfectly neutral, is added an equal volume of water. The alkaline gold
solution is prepared by dissolving one part of the double chloride of gold and
sodium in one hundred and twenty parts of water, and adding to that solution
two parts of caustic soda. The alkaline solution of nickel is prepared by
adding a slight excess of ammonia to a solution of one part of sulphate of
nickel in (40) forty parts of water.
I am aware that various plans have been proposed for protecting the

page_text: silvered surface of looking-glasses, as for example, by the application of a coat
or coats of varnish or paint, or by depositing thereon metallic coatings by the
ordinary electrotype processes; but these plans, including the use of the
common salts of copper which possess an acid reaction or cyanurets, cannot be
practically employed with advantage; I do not, therefore, claim their use.
But having thus described the nature and particulars of my said improvement,
I desire it to be distinctly understood that I do not confine myself to the exact
details herein described, as such may be varied or modified without departing
from the principle thereof; but I claim as new and of my Invention the use
of the double tartrate of oxide of copper and soda, potash or animonia, in the
electro-plating process, and the mode of protecting silvered surfaces of glass by
the agency of electricity in combination with a neutral solution of copper, aud
the alkaline solutions of metals, as herein described.
In witness whereof, I, the said Justus Baron Vou Liebig, have hereunto
set my hand and seal, this Twenty-first day of November, in the year
of our Lord One thousand eight hundred and fifty-eight.
JUSTUS VON LIEBIG. (...)