IMPROVEMENTS IN THE MANUFACTURE OF MAGNESIA AND OF MAGNESIAN REFRACTORY PRODUCTS
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 17th February 1881. A com-
munication from abroad by Jean Baptist Marie Prosper Closson, of Paris,
France.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN THE MANUFACTURE OF MAGNESIA
AND OF MAGNESIAN REFRACTORY PRODUCTS." [A communication from abroad
by Jean Baptiste Marie Prosper Closson, of Paris, France.]
'
In former Letters Patent, dated October 20th 1879, No. 4253, the present
inventor has described processes of manufacturing magnesia by means of dolomite
and certain chlorides often wasted, chlorides of iron, of manganese, waste waters of
sulphate of soda and chlorine works, natural chlorides of magnesium, such as those
of Stassfurt, &c., and also of residues already undergoing a transformation; and
which are employed so to speak in the process of manufacture, without prejudice
to the ultimate products of manufacture, such as chlorides of manganese in works
where the chlorine is regenerated, chloride of ammonium in the new processes of
making soda.
The Specification of the aforesaid Patent describes the details of the process
which may be performed at one operation in the case of chloride of ammonium or
bydrochloric acid, but which would be divided into two parts (or into 3 if the
separation of the deposits is counted) when operating on chlorides yielding a solid
deposit, for example, chloride of manganese.
When impure dolomites are used in these 'processes one can by slaking after
burning and mixing up and stirring with water cause the part most highly charged
with clay to deposit and separate, one can also by taking proper precautions in the
operations of precipitation and depositing cause the greater part of the clay and of
the oxide of iron to deposit in the first instance and separate them. One effects
in the same methods the separation of the sulphate of lime too often found in
dolomites; this separation may also be effected in the dry way by calcination
with charcoal or coal; thus in certain cases one may by the preliminary grinding
of the raw dolomite separate the impurities from it in great part at least by the
wet way, or also by classifying the dust by a current of air.
I have found that the operation is very much facilitated by the addition of a
little sugar (in practice molasses) to the liquors being worked with; by this means

page_text: a saccharate of lime is formed with the lime of the dolomite, and the same result is
attained as if the solubility of the lime were augmented; this saccharate is
decomposed as fast as it is formed by the chloride of magnesium, and yields
magnesia and chloride of calcium until the sugar being set free immediately reforms
saccharate of lime, &c.
I repeat, the result is the same as that which would be obtained by increasing
the solubility of the lime in water. One thus obtains in a more rapid manner a
very complete result, a very pure magnesia free from lime.
The same quantity of sugar may be employed repeatedly; it is recovered (except
the loss) in the liquors in which it forms an insoluble tribasic saccharate of lime,
moreover, this modification in the process enables much more concentrated liquors
to be used.
Having thus described the methods of separating the lime from the dolomite by
solubility in water and by treatment of the chlorides, I also claim the manufacture
of magnesia by the separation of the lime from the dolomite in the following
manner :-
In all parts of the manufacture of sugar or treatment of molasses in which
saccharates are formed I substitute calcined dolomite for lime and collect the
separated magnesia. No change is made in the ordinary operations of manu-
facture.
I also claim another method of operating, the principles of which I will describe
and illustrate by an example.
A sesquibasic do.,
A bibasic
A tribasic
2 (C¹¹¹¹¹), 3 Ca. O. 80.28 . . . 19-72.
Cà HA (1, Ca. O.. 75.34 .
do.,
do.,
C1: H"Q", 3 Ca. O
.
24.66.
67.06. 32-94.
.
Any one of these saccharates or mixtures in various proportions of each or any
of them is or are produced when one mixes lime with sugar or molasses. The
results vary according as there is an excess of sugar or of lime according to the
concentration of the liquors treated and also according to the temperature.
Of these saccharates some are soluble in water and some are insoluble, the
solubilities vary considerably with the temperature, or in other words the mixtures
of the saccharates or the total saccharate change or changes in composition, setting
free sugar or lime when the temperature varies, thus the tribasic sacccharate of
lime is very slightly soluble in the cold in pure water; its solubility increases when
the temperature rises, and finally is transformed at about 70° C. into monobasic
saccharate even in presence of an excess of lime.
Thus by heating nearly to ebullition an aqueous solution of monobasic saccharate
of lime, a tribasic saccharate is formed almost insoluble, and 2/3rds of the sugar is
set free and remains in solution in the liquor. By letting the liquor cool it becomes
clear, and the monobasic saccharate is reproduced.
The process of manufacture forming the subject of this Invention consists in
treating calcined dolomite with sugar so as to separate the lime by forming a
saccharate of lime, thus separating the magnesia. In modifying the external
conditions so as to form a saccharate more highly charged with a base, so as to set
free a part of the sugar which serves in a subsequent operation, in causing the
excess of lime to be deposited and in bringing the saccharate back to its former
condition, I will illustrate this process by an example, starting from monobasic
saccharate in order to arrive at tribasic saccharate.
I take 96 kilos. of calcined dolomite (which I assume to be pure for simplicity of
explanation), and containing 40 kilos. of magnesia and 56 kilos. of lime. By
mixing with proper stirring the 96 kilos. of powdered calcined dolomite with
342 kilos. of sugar dissolved in water I form 398 kilos. of soluble saccharate of lime
and a deposit is formed of the 40 kilos. of magnesia which I separate, I recover the

page_text: 398 kilos. of saccharate of lime, and add thereto 199 kilos. of the same saccharate,
making in all 597 kilos. I raise the temperature so as to form 255 kilos. of insoluble
saccharate of lime, which deposits and separates and sets free 342 kilos. of
sugar.
The 255 kilos. of tribasic saccharate of lime separated is brought back to
the ordinary temperature when it deposits 56 kilos. of lime, and there remains
199 kilos. of soluble saccharate.
Thus at the end of an operation I have on the one hand and separately 40 kilos.
of magnesia and 56 kilos. of lime, on the other hand 342 kilos. of sugar and
199 kilos. of soluble saccharate of lime.
The original conditions which prevailed at the commencement of the operation thus
obtain again and the operation may be recommenced; in other words I separate
the lime and the magnesia from the dolomite, obtaining on the one hand the
magnesia and on the other the lime. The saccharate of lime in consequence of
the change of temperature plays the part of a sponge absorbing the lime at a
certain temperature and giving it up at another.
In practice it is molasses which I use.
For simplicity of explanation I have given figures, notwithstanding their
liability to variation in practice, for according as the deposits are recovered each
time or are allowed to accumulate the proportions may be varied.
The operation is performed in various ways according to the quantities to be
produced. I operate either by simple deposit and washing, or by the filter press or
centrifugal hydro-extractor, or by simple filtration. According to circumstances
the liquors are transferred from one receptacle to another either by gravity or by
means of pumps.
The elevations of temperature are ordinarily effected by steam worms or coils.
In manufacturing magnesia by these processes the same difficulties are not
encountered as would be met with in applying the same methods to effect the
extraction of sugar from molasses, for in the latter case it is sought to effect the
complete regeneration of the sugar in a state of purity which presents difficulties,
the precipitates not always separating very easily and completely, the washings
being difficult, &c.
It is unnecessary to take the purity of the sugar into consideration. I operate
in a much more simple manner which enables me to apply the above mentioned
properties of saccharates of lime for the separation of lime and magnesia from
dolomite.
The magnesia obtained serves for many uses. Cement may be made of it, the
hydrate of magnesia becoming very hard. It may be used in painting as a
substitute for lime, oxide of zinc, &c.
I also employ it (and this is one of its principal applications) for the manufacture
of refractory products; in this connexion I employ new methods, which produce
commercial results which are also new; they have been described in the Specification
of a former Patent, dated December 21st 1880, No. 5365. In making refractory
products specially intended for use in the metallurgy of steel for which their
physical strength is of great importance, I have found it advantageous to some-
times add (in the form of phosphate of magnesia or other base) a little phosphoric
acid to the plastic mass, noth withstanding which addition the product is still
sufficiently refractory and has exceptional hardness.