IMPROVEMENTS IN THE MANUFACTURE OF CARBONIC ACID AND MAGNESIA
Year: 1888

page_text: I, HENRY LEFMANN, of 711 Walnut Street Philadelphia, State of Pennsyl-
vania, USA, Chemist, do hereby declare the nature of my invention for
"IMPROVEMENTS IN THE MANUFACTURE OF CARBONIC ACID AND MAGNESIA," and in whit
manner the sime is to be performed, to be particularly described and ascertained
in and by the following statement
My invention has reference to the manufacture of carbonic acid and extra heavy
magnesia for commercial purposes, and consists in cert un improvements fully set
forth in the following specification
Heretofore carbonic acid and magnesia of commerce have been made from distinct
substances and with no very satisfactory results The customary manner of producing
carbonic acid gas is to treat powdered lime stone or carbonate of lime with sulphuric
acid setting free the carbonic acid and producing calcium sulphate as a bye product
In the case of the manufacture of magnesia used in commerce the process is much
less direct It was customary to make a solution of magnesium salts from the rock
by treating it with acid then precipitating the magnesia by means of carbonate of
soda and after drying the precipitate, and igniting it These processes which arc
more or less complicated in their way, I dispense with and produce the two substances
in a most abundant manner from the same source and with the employment of very
simple apparatus Furthermore the magnesia produced by my process hereinafter
set out is extra heavy magnesia a far more valuable product than the precipitated
magnesia at present used commercially The native carbonate being much denser
than any artificial carbonate and magnesia being infusible at any temperature there
is no danger of converting it into lighter forms It remains heavier than any
magnesia produced from artificial carbonates, and by loss of carbonic acid the magnesia
becomes more readily soluble permitting the preparation of magnesia salts with more
ease and convenience than when made from carbonates directly
I am aware that it has been proposed to use magnesian limestone or dolomite for
the production of carbonic acid, but this will not answer my purpose for the
preparation of extra heavy magnesia, for the calcium oxide which would of necessity

page_text: be in the residue would interfere with the especial uses to which pure magnesi 15
apphed, and the processes for the removal of this calcium oxide would reconvert the
magnes into its ordinary very light condition, hence this process would be of no use
whatever, and could not produce a heavy pure magnesi for commercial purposes
Magnesian limestone is not the sime as magnesite is the mineralogical and chemical
qualities are very different It has also been proposed to make what is called magnesia
levis by heating so-called heavy carbonate of magnesia, but this is not the equivalent
of my process employing native magnesite, for the so-called heavy mignosian carbonate
18 precipitated material, requiring a special process to produce it, and the term heavy
181 comparative one as the magnesin is simply a little denser than that prepared by the
earliest processes My magnesia is so very heavy that all the above forms may properly
be considered light magnesi is
It has been the object of chemists to endeavor to
secure an extra heavy magnesia, and the use of the term heavy is herctofore used has
only been relative The effort of the art has been to secure a magnesia having a
dense, granular character the ordinary form being fluffy, and inconveniently light
By laboratory experiments slight gain in density was obtained, but it was far less
than th it which I can readily and directly produce by heating pure native magnesite,
and this extra heavy magnesia, which I hive succeeded in commercially producing
has many uses in the arts not heretofore possible with the lighter form as above
referred to
For certain purposes eg Cements, tooth-powder, magnes made by the processes
given in the chemical and pharmaceutical works is quite inapplicable, being too light
The magnesia produced by my process may be used with advantage in the manufacture of
ammonia, being heated with ammonium sulphate, yielding magnesium sulphate epsom
salts or with ammonium chloride, yielding magnesium chloride an ingredient of a
valuable cement These methods of producing important chemicals are impracticable
under the old method of mihing magnesia, because of the cost of it and the bulkiness
of the product By the process of heating magnesite is described, I secure a form of
magnesia for commercial purposes which is an improvement in the direction in which
the art has been striving that is towards overcoming the peculiar lightness in which
magnesia usually presents itself
In carrying out my invention I employ magnesite or magnesium carbonate which
after crushing, I place in a retort, from which the carbonic acid is distilled by
applying adequate temperature The carbonic acid gas so generated is more or less
pure and requires but little attention for purification The gas after leaving the
retort passes through the cooler to reduce its temperature and volume It then
enters a gasometer or holder where it is stored by which the gas may be supplied to
the compressor in a continuous manner From the holder the gas is led through a
dryer containing any well known drying medium and finally compressed into vessels
under sufficient pressure to liquify the dried and cooled gas With the decomposition
of the magnesite and the distillation of the carbonic acid we have the production of
magnesia, not of the kind commonly found in the market, but an extra heavy
magnesia which is a valuable compound, and has heretofore not been easy of
production
My process is extremely simple requiring for the production of its product only a
well known mineral, and means to apply the heat when taken in connection with the
necessary apparatus for storing the acid There are no complicated reactions
necessary nor are there several steps in the process required, and practice has shown
that the substances may be produced in the most abundant and speedy manner by
carrying out the hereindescribed invention
I employ a retort which is more or less similar to a retort used in the manufacture
of illuminating gas by the destructive distillation of coal, and is heated by a furnace
or otherwise so as to obtain a moderate temperature, which may be about 750 degrees
Centigrade The amount of heat required depends upon the pressure of the atmosphere
surrounding the magnesite while being decomposed, and we may say that the less the
pressure the less the heat required For this reason I prefer to so weight or otherwise
counterpoise the gas holder in such a manner that all back pressure is removed from

page_text: the retort, and if desired this may be carried to such an extent that there is an actual
suction produced in the retort causing the carbonic acid gas to piss off from the
magnes at an extremely low temperature To so weight or construct the holder
does not increase the cost of manipulation, and it certainly does not reduce the
consumption of coal or other hent giving substance used to heat the retort, and this
does appreciably reduce the cost both as to the manufacture of the carbonic acid gas
and the heavy magnesia
The gas after leaving the retort passes through the cooler by a pipe into an holder
as aforesaid and from the holder it pisses through a valved pipe to a dryer which
may be of any construction I find a good form to consist of a U shaped tube of
earthenware or substance not affected by acid which is filled with pumice stone
satur ited with sulphuric acid and over which the carbonic acid gas is drawn before
being compressed into the storage vessel whereby it is made perfectly anhydrous
After leaving the dryer the gas passes by a pipe to the compressor by which it is
compressed under a pressure, of about 500 pounds to the square inch, and thence into
the storage and shipping vessels
In place of sulphuric acid in the dryer chloride of calcium may be used, or anhydrous
copper sulphate may be employed
The heavy magnesia may be withdrawn from the retort as soon as the carbonic acid
has pissed off and it will be found very heavy and in the active condition So far as
the manuf icture of the magnesia is concerned the retort may be open and the carbonic
acid may be allowed to go to wiste
I do not limit myself to any particular apparatus in carrying out my invention as it
may be modified in various ways without changing its general features or the essential
principle of the process
Having now particularly described and ascertained the nature of my invention,
and in what inanner the same is to be performed, I declare that what İ
claim is
-
1st The process for the production of extra heavy magnesia consisting in subjecting
native magnesite to the action of heat
2nd The hereindescribed process for the simultaneous production of carbonic acid
and extra heavy magnesia consisting in subjecting native magnesite in a closed retort
to the action of heat which decomposes the native magnesite into carbonic aciu and
extri hey magnesia, then driwing off the cubonic acid gas from the retort,
and finally removing the extra heivy magnesia
3rd The hereindescribed commercial extra heavy magnesia formed from native
magnesite, as în improved article of manufacture