Improvements in the Manufacture of Artificial Rubies.
Year: 1896

page_text: Date of Application, 9th Sept., 1896
Complete Specification Left, 1st June, 1897-Accepted, 17th July, 1897
[Communicated from abroad by the Firm of GIN AND LELEUX, of Paris, in the
Republic of France.]
Improvements in the Manufacture of Artificial Rubies.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for Foreign
Patent Solicitors, 322, High Holborn, in the County of Middlesex, 6, Lord Street,
Liverpool, and 6, Bank Street, Manchester, both in the County of Lancaster, and
Lower Temple Street, Birmingham, in the County of Warwick, Civil Engineer, do
hereby declare the nature of this invention to be as follows:-
The present application for Letters Patent relates to a new process for the
manufacture of artificial rubies. The processes hitherto described, especially those
of Mr. Frémy invariably comprise the addition of a flux or mineralizing body which
induces the production of crystals of ruby. In the process of our invention the
constituent materials are placed together, and their combination and subsequent
crystallization is effected directly. The process consists essentially in heating to the
temperature of the electric arc, a mixture of suitable preparations of anhydrous
alumina and sexquioxide of chromium. These two bodies combine under the
influence of heat, and produce a compound, which, upon cooling possesses the form
of a hollow mass irregularly crystallized. The walls of the hollows are studded
with lamellar crystals of pink or violet rubies; the remainder of the mass is formed
of intermingled green crystals. By prolonging the electric heating the fluxed mass
of alumina and of chromite of alumina is rapidly vapourized, and by acting upon
this vapour we produce rubies in the form of large rhombohedric crystals. For
this purpose, the furnace in which the fusion, and the volatilization is effected is
provided with a cover into which is fixed a tube of refractory material which
discharges into a large condensing chamber. The vapours emitted by the liquid
mass contained on the hearth of the furnace are sublimated upon the walls of the
tube, and of the condensing chamber. Primarily only microscopic dust may be
obtained; if it be desired to produce large crystals it is necessary to cause a
mineralizing action to intervene. One such method consists in causing to pass
along the tube under slight pressure a mixture of damp air and hydrochloric acid,
which causes the formation of large pink crystals upon the walls of the tube. The
following method may also be employed :-A current of damp air is caused to pass
over the tube, at the same time as in the hearth of the furnace there are thrown at
frequent intervals small quantities of fluoride of aluminium or of cryolite which are
immediately volatilized under the influence of the watery vapour. The gaseous
fluoride is decomposed and hydrofluoric acid is produced at the same time as the
alumina and the chromite of aluminium crystallize in pink rhombohedric crystals
which attach themselves to the walls of the tube, and the size of which crystals
increases without interruption if the operation is properly conducted. The fusing
and volatilizing furnace preferably employed is provided with a cover in which a
tube is fixed preferably constructed of suitable refractory material, which tube
terminates in a large condensing chamber. The furnace has double electrodes the
first pair of which effects the fusion of the material whilst the second pair volatilise

page_text: it. The vapours given off from the fused mass which is on the hearth of the furnace
readily deposit upon the walls of the tube and of the condensing chamber.
The above described furnace provides a convenient method of carrying the
invention into effect, by way of example, but the same forms in itself no part of our
invention as any suitable electric furnace may be used.
Spinel rubies can be obtained by replacing in the furnace the above described
materials by a mixture in suitable proportions of anhydrous alumina, and caustic
magnesia.
Improvements in the Manufacture of Artificial Rubies.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 322, High Holborn, in the County of Middlesex, 6, Lord Street,
Liverpool, and 6, Bank Street, Manchester, both in the County of Lancaster, and
Lower Temple Street, Birmingham, in the County of Warwick, Civil Engineer, 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:-
The present invention relates to a process for the preparation of artificial rubies.
This process consists essentially in exposing a mixture consisting of anhydrous
alumina and sesquioxide of chromium in suitable proportions to the heat of the
electric arc. A good result is obtainable from the mixture of 97% alumina and
3% sesquioxide of chromium. The two bodies combine under the influence of the
heat and a product results which appears after cooling in the form of a porous
irregular crystallized mass. The sides of the holes are covered with lamellar
crystals of red or violet colour. The remaining part of the mass consists of
irregularly mixed green crystals. On causing the electric heating to continue
longer, the molten alumina and compound of aluminium and chromium is rapidly
volatilized and by acting upon this vapour the rubies are formed in the shape of
large rhombohedral crystals. For this purpose the furnace in which the fusing and
the volatilization is effected is provided with a tube of refractory material proceeding
from the cover of the furnace and delivering into a condensing chamber. This
condensing chamber is heated by means of a separate furnace in the manner of a
muffle to as near as possible 1500 degrees Centigrade. The vapours evolved from
the molten mass contained on the hearth of the furnace condense on the sides of the
tube and of the condensing chamber. The first product is only microscopic dust,
but the formation of larger crystals may be caused by inducing a mineralizing action
to take place. This action can be occasioned in various ways. There can for
instance be caused in the longitudinal direction of the tube under high pressure the
entrance of a mixture of moist air and vapour of hydrochloric acid. There are
then formed on the walls of the tube large red crystals. For the same purpose the
following operation can also be made use of :-
A stream of moist air is caused to pass into the tube whilst at the same time on
the hearth of the furnace small quantities of fluoride of aluminium or of cryolite are
introduced at short intervals, which are at once volatilized. By the action of the
vapour of water gaseous fluoride is liberated and hydrated fluoric acid is formed.
At the same time the alumina and chromium-aluminium compound crystallises in

page_text: red rhombohedral crystals which adhere to the walls of the tube and continuously
increase in size when the process is properly conducted.
In order more clearly to set forth the invention and the operation of the process
a drawing of the furnace preferably employed accompanies this specification. It
must however be specially noted that there is no intention of protecting this design
of the furnace as the same can be replaced by a suitable electric furnace of any
other construction. The furnace illustrated possesses two foci the one of these
effects the melting of the materials introduced whilst the other serves for the
volatilization of the molten mass. The mode of operating as well as the procedure
of the process is easily visible from the drawing. It should moreover be remarked
that the use of alternate current is preferable to the use of equal current. By the
application of the latter the mass at the first heating focus is electrolized and there
occurs a liberation of chromium in the form of metallic incrustations. After the
conclusion of the operation there is found in the furnace a kind of slaggy
incrustation of crystallized corundum, which moreover as the crystals are irregular
in form, discoloured and confusedly mixed with one another possesses no value as a
gem. But it can when ground serve with great advantage to replace emery for all
its industrial applications. As the preparation of rubies in large crystals is a tedious
and expensive business it is advisable to remove these crusts of molten corundum
at fixed intervals to make use of them in a suitable manner and to replace them by
fresh mixture. The value of the hard crusts thus obtained will easily cover the cost
for that portion of the mass which is volatilized and caused to crystallize out by
sublimation. Or in this invention the preparation of the above described mass
might be regarded as the principal object in view, and the large artificial rubies be
looked upon as a by-product.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed as communicated to me by my
foreign correspondents, I declare that what I claim is :-
1. A process for the preparation of artificial rubies and crystallized corundum
characterised by the melting and volatilizing of a mixture of alumina
preferably 97%) and of sesquioxide of chromium (preferably 3%) by means of an
electric furnace, and causing the said vapours to deposit in a condensing chamber
heated to about 1500 degrees in the presence of moist air and of hydrochloric acid
or of moist air and of a fluorine compound.
2. In the process set forth in Claim 1 the removal at fixed intervals of the fine
crystalline deposit formed in the crystalizing chamber, as well as of the molten
crystalline product of corundum which forms in the furnace, for the purpose of
utilising these two hard bodies in place of emery for appropriate technical
applications such as grinding, polishing and the like.
3. The application of the process set forth in Claim 1 for the simultaneous
production of a crystallized product of fusion of corundum for suitable industrial
purposes in such manner that the ingredients will serve for the evolution of the
ruby vapours are removed at fixed intervals, which crusts may be applied in the
same manner as the fine powder obtained from the condensing chamber to replace
emery for polishing purposes or for the construction of mill stones or rolls.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham,
Patent Agents for the Applicant.