a MENT OF MAGNESIA AND ITS COMBINATIONS IN MANUFACTURES
Year: 1863

page_text: LETTERS PATENT to Doctor Christian Gustav Clemm, of Dresden, in
"NEW EMPLOY-
the Kingdom of Saxony, Germany, for the Invention of a
MENT OF MAGNESIA AND ITS COMBINATIONS IN MANUFACTURES."
Sealed the 4th December 1863, and dated the 15th July 1863.

page_text: 1. Kieserit, a mineral which is found in considerable masses in the salt
mines of Stassfurth, in the Kingdom of Prussia, and in the Duchies of Anhalt,
is an isomeric modification of sulphate of magnesia, with one equivalent
of water (Mg 03 + HO), and has altogether different properties from the
latter.
2. The carbonate of magnesia, with three equivalents of water (MgO CO2
+3HO) dissolves with gypsum into sulphate of magnesia and carbonate
of lime.
3. By the calcination of sulphate of magnesia with charcoal, there are
obtained 2 volumes of sulphuric acid and volume carbonic acid, with a
residuum of magnesia.
4. The carbonic acid disengaged by the heat from mono or bi carbonate of
magnesia decomposes completely, in its primitive state, the mono and poly
sulphurets of potassium, sodium, and magnesium.
I. METHOD OF THE FABRICATION OF SULPHURIC ACID.
a. With kieserit.-The kieserit is reduced to powder, then purified from the
alkaline chlorides which it may contain by being washed in water, and after-
wards compressed in balls, cylindrical forms, or flat cakes, which are calcined
a sufficient time in a suitable apparatus into which steam is introduced. The
sulphuric acid disengages without being decomposed, and is received into
leaden chambers or other condensing apparatus. If the kieserit is mixed
with a little charcoal, it still more quickly disengages the sulphuric acid, but
part of it is thereby decomposed into sulphurous acid.
b. With the common sulphate of magnesia.-It is calcined in the same
manner as kieserit, with the addition of 10 to 15% of charcoal.
The gases
which are disengaged by this operation are composed of about 2 volumes of
sulphurous acid, and 1 volume of carbonic acid, and are transformed into
sulphuric acid in the leaden chambers after the ordinary method.
c. By means of different secondary products.
d. By means of sulphide of magnesia.-The salt already disengages at a
moderate heat (in furnaces or retorts hermetically closed) its sulphurous acid,
a small quantity, is transformed during this operation into sulphate of magnesia,
but this can be easily hindered by adding some per-centages of charcoal
before heating. By means of sulphuretted hydrogen gas, I burn it after the
method of Hunt, and oxidize the sulphurous acid. which results from its com-
bustion by the ordinary method in the leaden chambers.

page_text: II. METHOD OF THE FABRICATION OF SULPHATE OF POTASH, SULPHATE OF
SODA, THE DOUBLE SALTS OF THE SULPHATES, WITH THE SULPHATE OF
MAGNESIA, HYDROCHLORIC ACID, AND MAGNESIA.
Method of preparing sulphate of soda and its double salt with the sulphate
of magnesia.-By a dry way.-I pound very fine, and mix thoroughly 1
equivalent of chloride of sodium and 2 equivalents of kieserit, or as a thorough
mixture is difficult to obtain by means of a mill, or even by mixing vessels,
the purpose is better obtained by mixing together the two substances in the
least possible quantity of water, and evaporating the solution in a suitable
manner to the consistence of a thick paste. By the calcination of this
mixture in a muffle furnace under the influence of a current of steam, 1
obtain the double salt (MgO SO3 + NaO SO₂) and some magnesia, and there
is disengaged hydrochloric acid. I employ for this calcination furnaces of a
similar construction to those which are now used in the manufacture of
sulphuric acid for the oxidation of sulphuret of zinc (ZnS), and which are
as I know a combination of the muffle furnace with the common reverberatory
furnace. I calcine during some hours (as long a time as in the ordinary
preparation of sulphate) the mixture in the proper muffle furnace, by causing
to pass continually through it steam of water (by preference exceedingly
heated), and by raising the temperature towards the end to a blood red heat.
Then I push the mass on the second oven hearth, where it is exposed to the
immediate action of the flame, and where it can remain, while it is continually
stirred as long as in the first part of the furnace; so that the two. divisions of
Almost all the hydrochloric
the furnace are always simultaneously charged.
acid is disengaged from the muffle furnace, and I condense it in the ordinary
manner. The products of the combustion which come from the furnace can
serve to evaporate the dissolution of which I have before spoken. The evapora-
It is clear that it is
tion takes place in a muffle furnace heated from above.
not absolutely necessary to employ two equivalents of kieserit; if I employ less
than two equivalents I must calcine more strongly the mass. At the end of
the calcination the mass is composed of double salt (NaO SO, + MgO SO₂)
and magnesia. It can be used without further preparation in the fabrication
of soda, by the method described lower down. If I wish to prepare with this
mass the double salt (NaO SO, + MgO SO,), it is only necessary to separate it
from the magnesia by boiling water, and evaporate the solution to a state of
dryness in the reverberatory furnace.
To prepare pure (Hauber's salt by means of this double salt, there are two
different ways.
I saturate boiling water with the double salt (NaO SO, +

page_text: MgOSO), and keep the solution some time in a boiling state. This operation
is best performed in a reverberatory furnace heated from above, but I can
also apply, if it is possible for this purpose, the heat lost from the sulphate
furnace. The Glauber salt separates anhydrous under the form of a fine crys-
talline powder; it is immediately taken up, and easily washed in the gratings
which are behind the chimney, and higher than the cauldron where the
boiling takes place. The mother water contains all the sulphate of magnesia
with a minimum quantity of Glauber's salt. This sulphate of magnesia is
obtained also by the evaporation of the solution, and serves either for the dis-
engagement of sulphurous acid after the method given above, or for the trans-
formation of sea salt into Glauber's salt by means of Carre's apparatus, or
lastly, for the preparation of Glauber's salt by the humid way.
The double salt (NaO SO3 + MgO SO3) is dissolved with onc equivalent of sea
salt in water. This salt, if the solution is carried by a Carre's apparatus to a
temperature of + 28° F., is decomposed into sulphate of soda which crystallizes,
and chloride of magnesium which remains in solution. I have found that the
sulphate of magnesia in combination with the Glauber salt decomposes the sea
salt at a higher temperature than when in the free state.
By the humid way.-The decomposition of sea salt by kieserit, and con-
sequently the formation of the double salt (NaO SO, + MgO SO,) can also
take place by the humid way, that is to say, by the simple dissolution of
kieserit in a boiling solution of sea salt. I ought to remark that in this case
I can replace the second equivalent of kieserit by common sulphate of magnesia
(see above). I separate the double salt (NaO SO3 + MgO SO₂) from chloride
of magnesium by drying and crystallizing it; I employ it directly, or I make of
it Glauber's salt as given before.
By artificial cold.-If I dissolve equal equivalents of sea salt and kieserit
in the least quantity possible of boiling water, and expose this solution to a
temperature of + 24, 8° F, by means of Carre's apparatus, almost all the soda
precipitates to the state of Glauber's salt crystallized, and very pure. The
chloride of magnesium remains in solution with some small quantities of
chloride of sodium and sulphate of magnesia. The solution of chloride of
magnesium obtained as secondary products is employed in the preparation of
hydrochloric acid free from sulphuric acid. For this purpose I calcine it (in
the muffle furnace mentioned above) by subjecting it to the action of steam, a
moderate heat of 390° to 570° F. suffices to expel completely the hydrochloric
acid. A part of the chloride of magnesium is prepared in a dry state,
and will be brought in commerce under denomination "solid hydrochloric
acid." It is true it is not entirely dishydrated, it is impossible to get rid of the

page_text: water which it contains, except until there only remains 25%, but even with
this quantity of water it produces after the cooling a solid mass containing
about 57 per cent. of hydrochloric acid, and consequently gives out by calci-
nation about 14 hundredweight hydrochloric acid of 20° Beaume. This solid
hydrochloric acid is important for those who make a great consumption of
hydrochloric acid, so much the more because the magnesia that remains after
the calcination of chloride of magnesium is an excellent material for the pre-
paration of chloride combinations suitable for bleaching, for the fabrication
of refractory stones, for the precipitation of oxides of metals from their sul-
phates, and for the preparation of solid carbonic acid' which I describe lower
down.
Manner of preparing sulphate of potash and its double salt with the sul-
phate of magnesia.-I may apply to the decomposition of chloride of potas-
sium by means of kieserit all that has been mentioned in reference to chloride
of sodium, with modifications in the details. There are but 2 properties of
sulphate of potash which the sulphate of soda does not possess.
If I submit
a solution of kieserit in chloride of potassium to a steam pressure of 10 atmo-
spheres, all the potash is precipitated in the condition of sulphate free from
water. If I mix with a solution of sulphate of potash or of the double salt
(KO SO, + MgO SO3), which cannot be separated like the corresponding salt
of soda, 1 equivalent of chloride of sodium for each equivalent of sulphuric acid
contained in the solution, and that afterwards the mixture is carried to a
temperature of 0° to 4° F. by means of Carre's apparatus, the sulphate of
potash is transformed into chloride of potassium, which remains in solution,
and into sulphate of soda (with 10 HO.) The mother water is but a solution
of artificial carnallit. If I add to the solution of the double salt (KO SO3 +
MgO SO) only one equivalent of chloride of sodium, then I require but
a cooling to 40° F. to transform the sulphate of magnesia into Glauber's salt.
The product of the decomposition of chloride of potassium by means of kieserit
consisting of KO SO3 + MgO SO,, and of magnesia, is the best employed with-
out any farther preparation for the manufacture of potash.
Simultaneous preparation of the sulphates of soda and potash.-I may as
I see without any further explanation work simultaneously the mixtures of
chloride of potassium, of chloride of sodium, and of kieserit, such as they are
found naturally, according to the methods described for the purpose of obtaining
the sulphates of soda and of potash, or their double salts. In this case I sepa-
rate the 2 sulphates by. crystallization (or other similar operations), or else I
transform them simultaneously into carbonates (soda and potash) and sepa-
rate only these latter combinations. The separation of sulphates as well as of

page_text: III. METHOD OF MANUFACTURING SODA AND POTASH.
Preliminary remarks. In the manufacture of the sulphates as described
above, I obtain without expense as secondary products great quantities of
magnesia. The idea struck me to use the carbonate of magnesia in the same
way as the bicarbonate of soda for the decomposition of sulphur of sodium,
and this succeeded completely. I may consider the carbonate of magnesia,
and particularly the neutral carbonate (MgO CO, + 3HO) as solid carbonic acid.
This carbonate commences already far below 212° F. (at the contact of water)
to disengage pure carbonic acid, and loses at 570° F. all its carbonic acid, but
the residuum of magnesia absorbs the carbonic acid, even of very impure mix-
tures of products of combustion, as easily as the carbonate disengages its own;
it is above all the magnesia which has been heated with the carbonate of
the alkalies that possess this property in a very high degree. The preparation
and realization of this solid carbonic acid is a particular part of my Invention.
This preparation may become of great importance for the improvement of the
inethod of manufacturing soda of Kopp (Blyde and Benson), for the decom-
position of sulphur of barium for the making of beet sugar, and for many other
manufactures, especially for the preparation of sulphate of magnesia by means
of gypsum (according to the method described below). The carbonic acid
disengaged from carbonate of magnesia by a moderate heat exercises naturally
the same energetic action in its primary state upon the mono and poly
sulphurets of alkalies and earths, as the carbonic acid of bicarbonate of soda.
What has been said heretofore upon the decomposition of sulphurets of
sodium by means of my solid carbonic acid, and all that is going to be men-
tioned hereafter about the transformation of the sulphurets into carbonates,
is also applied with the sulphurets of potassium.
Description of the process of the proper fabrication. I add to the mixture
of magnesia and of sulphate of soda and sulphate of magnesia as it comes from
the decomposing furnace (sulphate furnace), 24 to 30 per cent. of charcoal
or caking coal, with the least quantity possible of cinder reduced into fine
powder, and I heat the mass in a reverberatory furnace of magnesian stone.
The reduction takes place under 1100° F., and the whole mass is completely
melted at 1300° F. at the utmost, whereas the mixture of Le Blanc requires
1850° F. and more for the fusion. I carry the melted mass into iron casks
which are hemetically closed. After the cooling it forms a solid, tender, and
porous mass, which contains some sulphuret of sodium, magnesia, some car-

page_text: bonate of soda, and of charcoal which was there in excess; I call this mixture
"the cast." During the fusion the sulphuric acid of sulphate of magnesia is
disengaged naturally under the form of sulphurous acid. If the gases which
are disengaged from the melting furnace are made to pass upon milk of
magnesia the sulphurous acid is absorbed, and forms sulphite of magnesia,
which is, as I have said above, a very suitable material for the preparation of
sulphurous acid. The magnesia which is enclosed in the cast absorbs carbonic
acid still more easily than free magnesia, if one exposes the cast, after having
watered it, to a current of carbonic acid, it absorbs it with a disengagement
of heat, and immediately disengages sulphuretted hydrogen gas. There is
formed gradually with a disengagement of sulphuretted hydrogen gas H S.
neutral carbonate of magnesia and bicarbonate of soda, as well as the well-
known combination of these two salts. When the disengagement of H. S
becomes weak the saturation by carbonic acid is finished, although the the mass
still contains some sulphur; to expel this sulphur entirely under the form of
HS, it is only necessary to heat the mass to about 570° F., by this means the
carbonic acid of the double salt and of the neutral carbonate of magnesia
becomes free and decomposes completely to their primitive state all the com-
binations of sulphur. If the sulphur of sodium is mixed, two equivalents .of
magnesia (as is the case in the cast of which I have spoken above), there is
then found in the carbonated cast a great excess of neutral carbonate of mag-
nesia and its double salts with the bicarbonate of soda; consequently there
only needs the expulsion of a part of the carbonic acid which it contains.,to
decompose all the combinations of sulphur which can already take place under
390° F. After this theoretical digression let us return to the process of
fabrication.
The casts come first into what I call the chambers of carbonization (mured
chambers or cylinders of zinc or any other metal), which can be hermetically
closed and contain in the interior several gratings of cast iron placed one
above the other, on which are put the casts.
A whole series of such chambers
are found upon the same plane, and are bound one to the other like the
reservoirs which serve for washing in lye the soda by methodical filtration.
The casts remain in this chamber 6 to 8 days, and are subjected during this
time to a methodical carbonization, so that the carbonic acid which escapes
from the first chambers mixed with H S is completely absorbed in the latter;
during this time the casts are frequently watered; it is also necessary that the
carbonic acid which is introduced should be moist. Each of the chambers is
in communication on one side with the apparatus which conducts pure and
moist carbonic acid, and on the other with the absorbing apparatus, wherein

page_text: sulphuretted hydrogen gas is absorbed. It is unnecessary to remark that I can
introduce successively in each of the chambers carbonic acid directly, and
likewise effect the escape of the gas successively by cach chamber.
As soon
as the carbonization is terminated I heat the casts from 390 to 570° F. This
operation can be effected even in the apparatus for carbonization if one intro-
duces there a current of highly heated steam, but it can also take place in
a second apparatus by means of heating from without (by means of heat
which escapes from a furnace). It seems to me superfluous to describe more
in detail the construction of this apparatus as well as that of the chambers for
carbonization. These constructions have quite a subordinate importance with
regard to the principal points of my discovery. Each engineer can execute
them in a different manner, and there is principally to remark that the casts
during the operation of carbonization and desulphuration should be protected
as much as possible against the current of air, an aim which can be obtained
in divers ways. The casts suitably carbonized with the precaution pointed to,
then heated to 570° F., are free from sulphur and hyposulphites; they are
composed of a rich soda at a high degree, and very pure, of magnesium, with
a little charcoal, but they only require to be heated by boiling water or steam
in order to give a highly concentrated solution of soda and a residuum of
magnesia. I need only to co-operate to a dry state this solution of soda
in a reverberating furnace, the floor of which is constructed of bricks of mag-
nesia in order to obtain a rich product in a high degree pure, and of the first
quality. I separate the residuum of magnesia from soda lye, with which it is
'still impregnated, by means of a centrifugal machine, or by the ordinary
washing in lye. It is appropriate for new operations. There is naturally
required for the carbonization of the cast a pure carbonic acid, free from air.
It is prepared by heating in a muffled furnace (of a similar construction to the
muffle furnace which serves for the preparation of the sulphate) of what I call
solid carbonic acid. I prepare the pure carbonate of magnesia by passing over
the residuum of magnesia, after its being washed in lye, the air of a stove. I
employ for this operation long mured chambers, in which are, upon iron rails,
some light carriages with several floors, on which I expose the hydrate of
magnesia mixed with morsels of charcoal. The magnesia absorbs the carbonic
acid in presence of steam as easily as the hydrate of magnesia. I direct
across these chambers, by means of a ventilator, the air of a stove after having
previously conducted it under the metallic floor of the chambers, and having
evaporated the water which had been previously poured therein. The
carriages remain from 8 to 10 days in these chambers, consequently much
longer than is necessary. I draw off daily at one extremity from the number

page_text: of carriages loaded with carbonate my daily use, and I push into the other
extremity as many carriages charged with caustic magnesia. I direct also, by
means of a Beale's exhauster, the carbonic acid which is disengaged from the
neutral carbonate of magnesia into the chambers for carbonization after having
previously mixed it with the requisite quantity of steam.
In order to avoid every surreptitious application which may be made of my
discovery without infringing directly on my Patent rights, I add here the
following modifications of my process which can be made use of:-I can replace
the mixture mentioned above of double salt NaO SO3 + MgO + SO, with
magnesia by a mixture of 1 equivalent of Glauber salt with 12 equi-
valent of magnesia or carbonate of magnesia for the manufacture of soda. In
this case it is suitable to add to the mixture before the fusion, besides the coal
necessary for the reduction, 20 to 30% of charcoal, anthracite, or coke, in
morsels of the size of a pea, in order to render the cast more porous. I can
also reduce the Glauber salt alone with charcoal; dissolve the sulphur of
sodium in a little water, mix the solution with some neutral carbonate of
magnesia, and afterwards heat the mass to 570° F. I can also mix the hot
solution of sulphur of sodium with the magnesia and let grow stiff, the
solution in its crystals, and then heat the solidified mass as I do the cast. It
is clear that I can prepare the magnesia I require in the above-mentioned
operations not only with kieserit and the chloride of magnesium, but also with
other materials, for instance, with magnesite, dolomite, and others. I apply
the sulphuretted hydrogen gas which I have obtained as a secondary product
by the decomposition of the sulphur of sodium and sulphur of potassium,
either as mentioned above by burning by means of the method of Hunt, or by
absorbing according to Spence's and Gossage's method by the oxide of
protoxide of iron or by employing it in the manufacture of sulphur.
IV. PROCESS OF PREPARING SULPHUR.
I decompose the sulphuretted hydrogen gas obtained as a secondary
product of the manufacture of soda, by sulphurous acid according to the known
methods of Persoz and Favre. I thus obtain in a pure state the sulphur
from the sulphuretted hydrogen gas as well as that of sulphurous acid. I may
also decompose the sulphuretted hydrogen gas according to Wagner's method
by means of sesqui chloride of iron.
V: METHOD OF PREPARING SULPHATE OF MAGNESIA.
I treat during a certain time, at a temperature of 122 to 158° F., some

page_text: VI. MET
OF TREPARI
SUBSTAN
FIT FOR THE EXTR
OF ORES.
I use for this purpose the chloride of magnesium which is formed in the
rubbish salts of Stassfurth, and which is also obtained by the decomposing
method mentioned above (see above about the form under which it may be
sent away).
The washed kieserit, which I call solid sulphuric acid;. I expel the acids of
these two salts by means of heating them in steam of water, and I direct
afterwards the acids in the form of steam to the ores. I may also very naturally
condense the acid vapours and use them under a liquid form for the extraction
of ores.
It has been long since known that poor ores can only be employed advan-
tageously in the neighbourhood of the mines from whence they are extracted,
and consequently one is compelled to transport the acids requisite for the
extraction to the mines. Railways or even good roads very seldom lead to them,
and then the transport of the acids in vitreous or earthen vessels is often
impossible. But the "solid acids" in question may (on the other hand) be
transported everywhere, since they may be forwarded in casks, or even, if
necessary, simply loaded upon open carts.
I must expressly notice that I consider the following processes as a help for
carrying into execution the aforesaid Invention:-
1. The decomposition of sulphate of magnesia with carbon.
2. Preparation of sulphate of magnesia by means of carbonate of magnesia
and gypsum.
3. Decomposition of chloride of magnesium with the help of heat and water.
4. Decomposition of sulphuretted hydrogen with sulphurous acid.
5. Employment of Carre's apparatus.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Christian Gustav Clemm in the Great Seal Patent Office
on the 14th January 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Doctor
CHRISTIAN GUSTAV CLEMM, of Dresden, in the Kingdom of Saxony, Germany,
send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of July, in the year of our Lord One
thousand eight hundred and sixty-three, in the twenty-seventh year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Christian Gustav Clemm, Her special licence that I, the said Christian
Gustav Clemm, my executors, administrators, and assigns, or such others as
I, the said Christian Gustav Clemm, 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
"NEW EMPLOYMENT OF MAGNESIA AND ITS COMBINATIONS IN MANUFACTURES," upon
the condition (amongst others) that I, the said Christian Gustav Clemm, 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 be
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 Christian Gustav Clemm, do hereby
declare the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement thereof, that is to say:-
Description of the different new processes for the manufacture of sulphur,
sulphuric acid, sulphate of potash, sulphate of soda, soda, potash, chloride of
potassium, and muriatic acid, and the uses to which the sub-products of them
may be applied for the manufacture of other chemical products.
PRELIMINARY EXPLANATIONS.
The new processes rest upon the following facts till now scientifically and
practically completely unknown, and consequently unused:---
1. Kieserit, a mineral which is found in considerable masses in the salt
mines of Stassfurth, in the Kingdom of Prussia, and in the Duchies of
Anhalt, is an isomeric modification of sulphate of magnesia, with
equivalent of water (MgO3 + HO), and has altogether different properties
from the latter.
onc
2. The carbonate of magnesia, with three equivalents of water (MgO
CO, +3HO) dissolves with gypsum into sulphate of magnesia and carbonate
of lime.

page_text: 3. By the calcination of sulphate of magnesia with charcoal, there are
obtained 2 volumes of sulphuric acid and I volume carbonic acid, with a
residuum of magnesia.
4. The carbonic acid disengaged by the heat from mono or bi carbonate of
magnesia decomposes completely, in its primitive state, the mono and poly
sulphurets of potassium, sodium, and magnesium.
I. METHOD OF THE MANUFACTURE OF SULPHURIC ACID.
(a.) With kieserit.-The kieserit is reduced to powder, then purified from
the alkaline chlorides which it may contain by being washed in water, and
afterwards compressed in balls, cylindrical forms, or flat cakes, which arc
calcined during a sufficient time in a suitable apparatus into which steam is
introduced. The sulphuric acid is liberated without being decomposed, and
is received into leaden chambers or other condensing apparatus. If the
kieserit is mixed with a little charcoal it disengages the sulphuric acid still
more quickly, but part of it is thereby decomposed in sulphurous acid.
•
(b.) With the common sulphate of magnesia.-It is calcined in the same
manner as kieserit, with the addition of 10 to 15% of charcoal.
The gases
which are disengaged by this operation are composed of about 2 volumes of
sulphurous acid and 1 volume of carbonic acid, and the former is transformed
into sulphuric acid in the leaden chambers after the ordinary method.
(c.) By means of different secondary products.
(d.) By means of sulphite of magnesia. The salt readily disengages at a
moderate heat (in furnaces or retorts hermetically closed) its sulphurous acid,
a small quantity is transformed during this operation into sulphate of
magnesia, but this can be easily hindered by adding some per-centages of
charcoal before heating.
(B.) By means of sulphuretted hydrogen gas.-I burn it after the method
of Hunt, and oxidize the sulphurous acid which results from its combustion
by the ordinary method in the leaden chambers.
II. METHOD OF THE MANUFACTURE OF SULPHATE OF POTASH, SULPHATE OF
SODA, THE DOUBLE SALTS OF THESE SULPHATES WITH THE SULPHATE
OF MAGNESIA, HYDROCHLORIC ACID, AND MAGNESIA
(A.) Method of preparing sulphate of soda and its double salt with the
sulphate of magnesia :-
(a.) By a dry way.-I pound very fine and mix thoroughly 1 equivalent
of chloride of sodium and 2 equivalents of kieserit, or as a thorough mixture
is difficult to obtain by means of a mill, or even by mixing vessels, the

page_text: purpose is better obtained by mixing together the two substances in the least
possible quantity of water, and evaporating this solution in a suitable manner
to the consistence of a thick paste. By the calcination of this mixture in a
muffle furnace under the influence of a current of steam I obtain the double
salt (MgO SO, + NaO SO), and some magnesia and hydrochloric acid is
disengaged. I employ for this calcination furnaces of a similar construction
to those which are now used in the manufacture of sulphuric acid for the
oxidation of sulphuret of zinc (Zn S), and which are a combination of the
muffle furnace with the common reverberatory furnace. I calcine during some
hours (as long a time as in the ordinary preparation of sulphate) the mixture
in the proper muffle furnace, causing steam (by preference highly heated)
to pass continually through it, and raising the temperature towards the end to
a blood red heat. Then I push the mass on the second oven hearth, where it
is exposed to the immediate action of the flame, and where it can remain,
while it is continually stirred as long as in the first part of the furnace, so that
the two divisions of the furnace are always simultaneously charged. Almost
all the hydrochloric acid is disengaged from the mufle furnace, and I con-
dense it in the ordinary manner. The products of the combustion which
come from the furnace can serve to evaporate the solution of which I have
before spoken. The evaporation takes place in a furnace heated from above.
It is clear that it is not absolutely necessary to employ 2 equivalents of
kieserit; if I employ less than 2 equivalents, it is necessary to calcine the
mass more strongly. At the end of the calcination the mass is composed of
double salt (NaO SO3 + MgO SO,) and magnesia. It can be used without
further preparation in the manufacture of soda by the method described lower
down. If I wish to prepare with this mass the double salt (NaO SO3 +
MgO SO) it is only necessary to separate it from the magnesia by boiling
water, and evaporate the solution to a state of dryness in the reverberatory
furnace.
.To prepare pure Glauber's salt by means of this double salt there are two
different ways.
(d.) I saturate boiling water with the double salt (NaO SO, +MgO SO₂),
and keep the solution for some time in a boiling state. This operation is best
performed in a reverberatory furnace heated from above, but I can also apply
for this purpose the heat lost from the sulphate furnace. The Glauber salt
separates in an anhydrous state as a fine crystalline powder; it is immediately
taken up and easily washed in the gratings which are behind the chimney,
and higher than the cauldron where the boiling takes place.
The mother water contains all the sulphate of magnesia, with but a small

page_text: quantity of Glauber's salt. This sulphate of magnesia is obtained also by the
evaporation of the solution, and serves either for the disengagement of sul-
phorous acid after the method given above, or for the transformation of sea
salt into Glauber's salt by means of Carre's apparatus; or, lastly, for the pre-
paration of Glauber's salt by the humid way.
(B.) The double salt (NaO SO3 + MgO SO3) is dissolved with one equi-
valent of sea salt in water. This salt, if the solution is carried by a Carre's
apparatus to a temperature of + 28° Fahrenheit, is decomposed into sulphate
of soda which crystallizes, and chloride of magnesium which remains in
solution. (I have found that the sulphate of magnesia in combination with
the Glauber salt decomposes the sea salt at a higher temperature than when
in the free state.)
(b.) By the humid way. The decomposition of sea salt by kieserit, and
consequently the formation of the double salt (NaO ṢО, + MgO SO.) can
also take place by the humid way, that is to say, by the simple solution of
kieserit in a boiling solution of sea salt. I ought to remark, that in this case
I can replace the second equivalent of kieserit by common sulphate of mag-
nesia. (See above.)
I separate the double salt (NaO SO3 + MgO SO₂) from chloride of magnesium
by drying and crystallizing it. I employ it directly, or I make of it Glauber's
salt, as given in (a).
(c.) By artificial cold.--If I dissolve equal equivalents of sea salt and kieserit
in the least quantity possible of boiling water, and expose this solution to a
temperature of + 24.8° Fahrenheit by means of Carre's apparatus, almost all
the soda precipitates in the state of Glauber's salt crystallized, and very pure;
the chloride of magnesium remains in solution with some small quantities of
The solution of chloride of
chloride of sodium and sulphate of magnesia.
magnesium obtained as secondary product by (b) and (c) is employed in the
preparation of hydrochloric acid, free from sulphuric acid. For this purpose I
calcine it (in the muffle furnace mentioned above) by subjecting it to the
action of steam, a moderate heat of 390 to 570° F., suffices to expel com-
pletely the bydrochloric acid. A part of the chloride of magnesium is
prepared in a dry state, and will be brought into commerce under the denomi-
nation "solid hydrochloric acid." It is true it is not entirely anhydrous
it is impossible to get rid of all the water which it contains, but the quantity
can be reduced until there only remains 25%, with this quantity of water it
produces after the cooling a solid mass containing about 57 per cent. of
hydrochloric acid, which it gives off by calcination, about 14 hundredweight
hydrochloric acid of 20° Beaume. This solid hydrochloric acid is important

page_text: and the OTSO Decause the mag
nesia that remains after the calcination of the chloride of magnesium is an
excellent material for the preparation of chlorine combinations suitable for
bleaching, for the manufacture of refractory stones, for the precipitation of
oxides of metals from their sulphates, and for the preparation of "solid car-
bonic acid," which I describe lower down.
B. MANNER OF PREPARING SULPHATE OF POTASH AND ITS DOUBLE SALT
WITH THE SULPHATE OF MAGNESIA.
I may apply to the decomposition of chloride of potassium by means of
kieserit all that has been mentioned at (A) (a) in reference to chloride of
sodium, with modifications in the details. There are but 2 properties of sul-
phate of potash which the sulphate of soda does not possess.
(a.) If I submit a solution of kieserit in chloride of potassium to a steam
pressure of 10 atmospheres, all the potash is precipitated in the condition of
sulphate free from water.
(b.) If I mix with a solution of sulphate of potash or of the double salt
(KO SO, + MgO SO), which cannot be separated like the corresponding
salt of soda, onc equivalent of chloride of sodium for each equivalent of
sulphuric acid contained in the solution, and afterwards carry the mixture to
a temperature from 0° to 4° Fahrenheit by means of Carre's apparatus, the
sulphate of potash is transformed into chloride of potassium, which remains in
solution, and into sulphate of soda (with 10 HO). The mother water is but
a solution of artificial carnallit. If I add to the solution of the double salt
(KO SO, +MgO SO₁) only one equivalent of chloride of sodium, then I require
but a cooling to 40° Fahrenheit to transform the sulphate of magnesia into
Glauber salt.
The product of the decomposition of chloride of potassium by means of
kieserit, consisting of KO SO + Mg OSO, and of magnesia, is best employed
without any further preparation for the manufacture of potash.
(c.) Simultaneous préparation of the sulphates of soda and potash.-I may
work simultaneously the mixtures of chloride of potassium, of chloride of
sodium, and of kieserit, as they are found naturally, according to the methods
described at (A) and (B) for the purpose of obtaining the sulphates of soda
and of potash or their double salts. In this case 1 separate the 2 sulphates by
crystallization (or other similar operations), or else I transform them simul-
taneously into carbonates (soda and potash), and separate only these latter
combinations. The separation of sulphates as well as of carbonates of potash
and of soda are well known operations which offer no difficulty.
'

page_text: III. METHOD OF MANUFACTURING SODA AND POTASHI.
Preliminary remarks. In the manufacture of the sulphates, as described
above, I obtain without expense as secondary products great quantities
of magnesia. The idea struck me to use bicarbonate of magnesia in the same
way as the bicarbonate of soda for the decomposition of sulphuret of sodium,
and this succeeded completely. We may consider the carbonate, of
magnesia, and particularly the neutral carbonate, MgO CO, +3HO, as
solid carbonic acid. This carbonate commences far below -212°
Fahrenheit (on contact with water) to disengage pure carbonic acid,
and loses at 570° Fahrenheit all its carbonic acid, but the residuum of
magnesia absorbs the carbonic acid, even of very impure mixtures of
products of combustion, as easily as the carbonate disengages its own; it is
particularly the magnesia which has been heated with the carbonates of the
alkalies that possesses this property. The preparation of this solid carbonic
acid is an important part of my Invention. This preparation may become of
great importance for the improvement of the method of manufacturing soda of
Kopp (Blyde and Benson), for the decomposition of sulphuret of barium, for
the making of beet sugar, and for many other manufactures, especially for the
preparation of sulphate of magnesia by means of gypsum (according to the
method described below). The carbonic acid disengaged from carbonate of
magnesia by a moderate heat exercises naturally the same energetic action in
its primary state upon the mono and poly sulphurets of alkalies and carths as
the carbonic acid of bicarbonate of soda.
What has been said heretofore upon the decomposition of sulphurets of
sodium by means of my solid carbonic acid, and all that is going to be men-
tioned hereafter about the transformation of the sulphurets into carbonates, also
applies to the sulphurets of potassium.
DESCRIPTION OF THE PROCESS OF MANUFACTURE.
I add to the mixture of magnesia and of sulphate of soda, or of sulphate of
soda and sulphate of magnesia as it comes from the decomposing furnace
(sulphate furnace) 24 to 30 per cent. of charcoal or coking coal (with the least
quantity possible of ash) reduced into fine powder; and I heat the mass in a
reverberatory furnace of magnesian stone. The reduction takes place under
1100° Fahrenheit, and the whole mass is completely melted at 1300° Fahren-
heit at the utmost, whereas the mixture of Le Blanc requires 1850° Fahrenheit
and more for the fusion. I carry the melted mass into iron casks, which are
hermetically closed; after the cooling it forms a solid but porous mass, which

page_text: contains some sulphuret of sodium, magnesia, some carbonate of soda, and
charcoal which was there in excess; I call this mixture "the cast." During
the fusion, the sulphuric acid of sulphate of magnesia is disengaged naturally
under the form of sulphurous acid. If the gases which are disengaged from
the the melting furnace are made to pass in contact with milk of magnesia, the
sulphurous acid is absorbed and forms sulphite of magnesia, which is, as I have
said above, a very suitable material for the preparation of sulphurous acid. The
magnesia which is inclosed in the cast absorbs carbonic acid still more easily
than free magnesia, if one exposes the cast, after having watered it, to a current
of carbonic acid, it absorbs it with this production of heat, and immediately
disengages sulphuretted hydrogen gas. There is formed gradually with a
disengagement of sulphuretted hydrogen gas (HS) neutral carbonate of
magnesia and bicarbonate of soda, as well as the well-known combination of
these two salts. When the disengagement of HS becomes slow, the satura-
tion by carbonic acid is finished, although the mass still contains some sulphur;
to expel this sulphur entirely under the form of HS. it is only necessary to
heat the mass to about 570° Fahrenheit, by this means the carbonic acid of
the double salt and of the neutral carbonate of magnesia is set free and
decomposes completely all the combinations of sulphur. If the sulphuret of
sodium is mixed with 2 equivalents of magnesia (as is the case in the cast
of which I have spoken above) there is then found in the carbonated cast a
great excess of neutral carbonate of magnesia and its double salts with the
bicarbonate of soda; consequently there only needs the expulsion of a part of
the carbonic acid which it contains to decompose all the combinations of
sulphur, which will take place under 390° Fahrenheit. After this theoretical
digression, let us return to the process of manufacture.
The casts come first into what I call the chambers of carbonization (walled
chambers or cylinders of zinc or any other metal) which can be hermetically
closed, and contain in the interior several gratings of cast iron placed one
above the other, on which are put the casts. A whole series of such chambers
are arranged upon the same plane, and are bound one to the other, like the
reservoirs which serve for washing the soda in lye by methodical filtration.
The casts remain in this chamber from 6 to 8 days, and are subjected during
this time to a methodical carbonization, so that the carbonic acid which escapes
from the first chambers mixed with sulphuretted hydrogen (HS) is completely
absorbed in the latter; during this time the casts are frequently watered; it is
also necessary that the carbonic acid which is introduced should be moist.
Each of the chambers is in communication on one side with the apparatus

page_text: which conducts pure and moist carbonic acid, and on the other with the
absorbing apparatus, wherein sulphuretted hydrogen gas is absorbed. It is
unnecessary to remark that I can introduce carbonic acid successively into
each of the chambers directly, and likewise effect the escape of the gas
successively by each chamber. As soon as the carbonization is terminated. I
heat the casts to between 390 and 570° Fahrenheit. This operation can
be effected even in the apparatus for carbonization, if a current of highly
heated steam be introduced there, but it can also take place in a second
apparatus, by means of heating from without (by means of heat which escapes
from a furnace).
It seems to me superfluous to describe more in detail the construction of
These
this apparatus, as well as that of the chambers for carbonization.
constructions have quite a subordinate importance with regard to the principal
points of my discovery. Each engineer can execute them in a different manner,
and there is principally to remark that the casts during the operation of
carbonization and desulphurization should be protected as much as possible
against the current of air, an aim which can be attained in divers ways.
The casts suitably carbonized with the precautions pointed to, then heated to
570° Fahrenheit, are free from sulphur and hyposulphites; they are composed
of a rich soda and very pure of magnesia with a little charcoal, but they only
require to be heated by boiling water or steam, in order to give a highly con-
centrated solution of soda and a residuum of magnesia. I need only to
evaporate to a dry state this solution of soda in a reverberating furnace, the
floor of which is constructed of bricks of magnesia, in order to obtain a rich
product in a high degree pure, and of the first quality. I separate the
residuum of magnesia from soda lyc, with which it is still impregnated, by
means of a centrifugal machine, or by the ordinary washing in lye. It is
appropriate for new operations. There is naturally required for the carboni-
zation of the cast a pure carbonic acid free from air. It is prepared by heating
in a muffled furnace (of a similar construction to the muffle furnace which
serves for the preparation of the sulphate) what I call solid carbonic acid. I
prepare the pure carbonate of magnesia by passing the air of a stove over the
residuum of magnesia after its being washed in lye. I employ for this
operation long walled chambers, in which are, upon iron rails, some light
carriages with several floors, on which I expose the hydrate of magnesia mixed
with small pieces of charcoal. The magnesia absorbs the carbonic acid in
presence of steam as easily as the hydrate of magnesia. 1 direct across these
chambers, by means of a ventilator, the air of a stove, after having previously

page_text: conducted it under the metallic floor of the chambers, and having evaporated
the water which had been previously poured therein. The carriages remain
from 8 to 10 days in these chambers, consequently much longer than is
necessary. I draw off daily at one extremity from the number of carriages
loaded with carbonate the daily use, and I push into the other extremity as
many carriages charged with caustic magnesia. I direct also, by means of a
Beale's exhaustor the carbonic acid, which is disengaged from the neutral car-
bonate of magnesia into the chambers for carbonization, after having previously
mixed it with the requisite quantity of steam. In order to avoid every surrep-
titious application which may be made of my .discovery without infringing
directly on my Patent rights, I add here the following modifications of. my, pro-
cess which can be made use of :-
(1.) I can replace the mixture mentioned above of double salt
NaO SO,+ MgO SO, with magnesia, by a mixture of one equivalent of
Glauber salt with from 1 to 2 equivalents of magnesia or carbonate of mag-
nesia for the manufacture of soda. In this case it is suitable to add to the
mixture, before the fusion, besides the coal necessary for the reduction, 20 to
30% of charcoal, anthracite, or coke, in pieces of the size of a pea, in order
to render the cast more porous.
(2.) I can also reduce the Glauber salt alone with charcoal, dissolve the
sulphuret of sodium in a little water, mix the solution with some neutral car-
bonate of magnesia, and afterwards heat the mass to 570° Fahrenheit.
(3.) I can also mix the hot solution of sulphuret of sodium with the mag-
nesia, and let the solution grow stiff in crystallizing, and then treat the solidified
mass as I do the cast.
(4.) It is clear that I can prepare the magnesia I require in the above-
mentioned operations not only with kieserit and the chloride of magnesium
but also with other materials; for instance, with magnesite, dolomite, and
others.
I apply the sulphuretted hydrogen gas which I have obtained as a secondary
product, by the decomposition of the sulphuret of sodium and sulphuret of
potassium, either as mentioned above by burning it by means of the method
of Hunt, or by absorbing it according to Spence's and Gossage's methods by
the oxide of protoxide of iron, or by employing it in the manufacture of
sulphur..

page_text: of Persoz and Favre; I thus obtain in a pure state the sulphur from the sul-
phuretted hydrogen gas, as well as that of sulphurous acid; I may also decom-
pose the sulphuretted hydrogen gas according to Wagner's method by means
of sesquichloride of iron.
V. METHOD OF PREPARING SULPHATE OF MAGNESIA.
I treat, at a temperature of 122 to 158° Fahrenheit, gypsum powdered
very minutely, and suspended in water with neutral carbonate of magnesia
(MgO CO₂ + 3HO) by stirring continually. A solution of sulphate of magnesia
and a residuum of carbonate of lime are then formed.
VI. METHOD OF PREPARING SUBSTANCES FIT FOR THE EXTRACTION OF ORES.
I use for this purpose,―
(a.) The chloride of magnesium, which is found in the rubbish salts of
Stassfurth, and which is also. obtained by the decomposing method mentioned
above (see above about the form under which it may be sent away).
(b.) The washed kieserit, which I call solid sulphuric acid; I expel
the acids of these two salts by means of heating them in steam,, and I direct
afterwards the acids in the form of vapour on to the ores.
I may also
condense the acid vapours and use them in a liquid form for the extraction of
ores.
It has been long since known that poor ores can only be employed advantag-
eously in the neighbourhood of the mines from whence they are extracted,
and consequently one is compelled to transport the acids requisite for the
extraction to the mines. Railways or even good roads very seldom lead to
them, and then the transport of the acids in vitreous or carthy vessels is often
impossible. But the "solid acids" in question may (on the other hand) be
transported every where, since they may be forwarded in casks, or even if
necessary simply loaded upon open carts.
I must expressly notice that I consider the following processes as a help for
carrying into execution the aforesaid Invention :--
1. The decomposition of sulphate of magnesia with carbon.
2. The preparation of sulphate of magnesia by means of carbonate of mag-
nesia and gypsum.
3. The decomposition of chloride of magnesium with the help of heat and
water.
4. The decomposition of sulphuretted hydrogen with sulphurous acid.
B The amplament of Carre's annaratus.

page_text: use of these nve processes.
In witness whereof, I, the said Christian Gustav Clemm, have hereunto
set my hand and seal, this Twentieth day of November, in the year of
our Lord One thousand eight hundred and sixty-three.
DR. CHRISTIAN GUSTAV CLEMM. (L.S.)