Improvements in the Method of and Apparatus for Manufacturing Hydrated Phosphates and in Recovering Bye Products therefrom.
Year: 1887

page_text: Date of Application, 14th Dec., 1887
Complete Specification Left, 10th Aug., 1888
Complete Specification Accepted, 14th Dec., 1888
Improvements in the Method of and Apparatus for Manufacturing
Hydrated Phosphates and in Recovering Bye Products therefrom.
I, LOUIS GUSTAVE GHILAIN DAUDENART, of Brussels, in the Kingdom of Belgium,
Lieutenant General (Retired), do hereby declare the nature of this invention to be
as follows:-
In the new mode of making phosphate which forms the subject of the present
invention a new arrangement of gas generating furnace is employed of which
the following is the specification.
In the annexed drawings, the furnace is represented. Figure 1 is a longitudinal
section of the furnace on line A B of Figure 2.
Figure 2 is a section following the lines CD EF G H of Figure 1.
Figure 3 is a section following the line IJ of Figure 1.
Figure 4 section following the line K L of Figure 1.
Figure 5 section following the line QR of Figure 1.
Figure 6 section following the line ST of Figure 1.
Figure 7 section following the line M N of Figure 2. and
Figure 8 section following the line OP of Figure 2.
a is the gas generator. b entry of combustible gas into the circular distribution
flue. c circular distribution flue of combustible gas. d wall separating the flue c
from the flue e where the combustible gas is brought to encounter the air in Q and
to be inflamed. fentry of the air into the furnace. g circular distribution flue for
the air. h walls separating the flue g from the circular flue i where the air arrives to
exit at j and to mix in Q with the combustible gases which it burns. k large arched
flue giving to the exterior air a second entry into the furnace. arched spaced
conducting the air into the circular flue m. m' circular distribution flue for air
entering at o. n walls separating the flue m of the circular flue o where the air
enters to go out at p and to mix in Q with the combustible gas which it inflames.
metallic sole formed of plates of cast iron. It is upon this sole that the chloride
of magnesium arrived at the desired degree of concentration is projected in the form

page_text: of liquid dust in order to be decomposed and to produce hydrochloric acid which
distilling with the vapour of water is condensed by refrigeration by means of a worm
where it exists combined with water at the density of 1094. s arches or bridges of
refractory bricks upon which are supported cast iron bars destined to transmit the
heat to the plates of cast iron constituting the sole, and to prevent the direct contact
of these plates with the flame. The metallic sole can be replaced if necessary by a solo
of refractory bricks. t circular wall serving also as a support to the plates of cast
iron or to the refractory bricks. central exit flue of the burnt air. v flue for
making the hot gas to circulate under that part of the sole not heated directly.
w flue conducting the hot gases under the roof b¹ and thence to the chimney.
opening for drawing the fire of the gas generator. y grate for supporting the fuel.
z movable valve for giving access to the air dilated by the instantaneous combustion
of the combustible gases at the time of lighting, a exit of gas produced by the
decomposition of the chloride of magnesium which go off to the condenser. roof
receiving the chloride of magnesium arrived at the degree of concentration and
coming from the evaporating apparatus.
N. The letters above are shown as far as necessary upon the Figures 1 to 8 which
Figures describe all the furnace for the decomposition of chloride of magnesium
by means of lime.
Whatever be the composition of the phosphate to be treated, it is submitted first of
all to a cold washing in ordinary water which has for its object to take up the
soluble particles in the water and to separate at the same time by decantation the
insoluble parts of little density (ochreous clay, carbonate of lime, called in French
"folle-farine," silica, sand etcetera) which can be removed without taking with them
phosphate. This operation terminated there remains a composition essentially formed
of tricalcic phosphate, of carbonate of lime combined with phosphate or not, of silica,
of sand, various insoluble matters which taken altogether may be considered as a
first product which will be called hereafter Ph L and which our correspondent calls
"phosphorite lavée" (washed phosphorite).
The process of making hydrated bicalcic phospate comprises the following
operations based upon the chemical reactions which are given hereafter in the form
of formulae.
A. Treatment of the first product by diluto hydrochloric acid giving a solution
principally formed of chloride of calcium and acid phosphate of lime.
Po 3 Ca On (Co² Ca O) + L (silica, sand, matters inert in soluble matters
etc)+n+2) Cl H, 16 Ho} = Po Ca O. 2 HO + (n + 2) Cl Ca + (n + 2)
16 HOn (HO) + n CO²↑ + Lu.
Po 3 CaO+n (Co² Ca O) + L (silica, sand, matters inert in soluble matters
etc)+n+2) C1 H, 16 Ho} Po Ca O. 2 HO+ (n + 2) Cl Ca + (n + 2)
16 HO+n (TQ)+n CO + L.
B. Treatment of the hydrochloric solution of phosphorite by hydrated magnesia and
2 (Po Ca O 2 Ho) + 2 (n + 2) cl Ca + 2 (n + 2) 16 Ho + 2 n (HO) + 2
(Mg O, Ho)=2 (PO³, 2 Ca O. HO) + 2 (Cl Mg) + (2n+2) cl Ca + 2 (n + 2)
C. Treatment of the neutral resultant solution and principally formed of chloride
of calcium and of chloride of magnesium by neutral carbonate of magnesia and of acid
carbonate until complete transformation of the chloride of calcium into dissolved 4
chloride of magnesium and into insoluble carbonate of lime which separate the one
from the other.
2 (cl Mg) + (2
+(2n+2) Co
+ 2) cl Ca + 2 (n + 2) 17 HO + (2 n + 2) Co² Mg O
2 (n+2) cl Mg + (2n+2)-Co² Ca-0-+-(2-n-+ 2) 602-

page_text: D. Evaporation of the solution of chloride of magnesium until there is no more
than one equivalent of water for one equivalent of magnesium. This evaporation
being necessary inasmuch as one has added water after the B operation in order to
wash the precipitated phosphate.
E. Decomposition by heat of hydrated chloride of magnesium into hydrochloric
acid for one part and into anhydrous magnesia for the other part, then condensation
of the aid into the state of cl H, 16 HO.
than one equivalent of water for one equivalent of magnesium. This evaporation
being necessary inasmuch as one has added water after the B operation in order to
wash the precipitated phosphate.
E. Decomposition by heat of hydrated chloride of magnesium into hydrochloric
acid for one part and into anhydrous magnesia for the other part, then condensation
of the aid into the state of cl H, 16 HO.
2 (n+2) Cl Mg + 2 (n + 2) 17 HO: = 2 (n+2) (Cl H 16 HO) + 2 (n + 2)
Mg Ò.
The proceeding operations will be now passed in review, formulae under the
heads A. B. C. D. É.
A. The first operation is made by means of dilute hydrochloric acid, It is
employed at the density of about 1.094 marking about 13° on the areometer of
Baumé and having the composition of cl H 16 HO. All the acid employed ought
to be converted into chloride of calcium and the phosphate into acid phosphate of
lime. To obtain this result there ought to be an excess of the first product and the
process ought to be stopped when a portion of the liquor filtered and treated by a
drop of ammonia in solution gives a precipitate which will not dissolve by further
agitation of the liquor.
B. The second operation consists in adding to the solution of phosphorite,
hydrated magnesia newly precipitated and perfectly divided until complete neutrali-
zation, that is to say until the liquor no longer alters litmus paper (papier bleu de
tournesol) and is no longer alkaline. The hydrated magnesia presents over hydrated
lime this important advantage, that with magnesia it at once forms a neutral
phosphate of hydrated magnesia (Pho³ 2 MgO HO) which is soluble in water and
which consequently can only give with the chloride of calcium in solution in the
water bicalcic hydrated phosphate, whilst that with lime tricalcic phosphate is often
formed which diminishes thus the mercantile value of the precipitate which in order
to constitute an immediately assimilable manure ought to present itself under the
form of hydrated bicalcic phosphate.
It is important further to remark that although the precipitation by lime is publicly
known the entire set as a whole of the chemical reactions which constitute this
process over the manufacture of precipitated phosphate and all the revivication of the
reagents employed is believed to be new, and that either lime or magnesia is used as a
precipitating agent.
C. The complete transformation of chloride of calcium into chloride of magnesium
and into carbonate of lime is obtained by means of carbonate of magnesia acting
under pressure with an excess of carbonic acid. It is generally known that for
carbonates under pressure it is necessary to use pure carbonic acid, the effect of
the pressure becoming insignificant when this acid is mixed with a strong preparation
of inert gas, such as those which are obtained by the combustion of carbon in
industrial furnaces. Since then if one operates upon the magnesia in suspension in
a solution of chloride of calcium, the quantity of pure carbonic acid acting under
pressure becomes considerable since to act completely upon the chloride of calcium
all the corresponding magnesia ought to be transformed into carbonate. The result
is a great loss of time otherwise a great expenditure of pure carbonic acid. To avoid
these double inconveniences the hydrate of magnesia is transformed first into neutral
carbonate of magnesia and this is exposed to the action of the gas resulting from
combustion of coal in industrial furnaces gas generators or others or even to the
action of carbonic acid which has been mixed with any gases not powerful to prevent
its action or to destroy it, the carbonic acid under pressure of two or three
atmospheres is made to react upon carbonate of magnesia in suspension in a solution
of chloride of calcium. In these conditions the carbonetation of the lime takes place
rapidly and the quantity of carbonic acid employed is at a minimum. Further the

page_text: pure carbonic acid which has eventually traversed the liquid without being absorbed
returns to the gasometer to be extracted anew from it and to be employed again
without causing the least interruption to the work of the gas pump employed, for
this purpose.
This new manner of proceeding brings about at the same time a great economy of
time and of money, the production of the pure carbonic acid being relatively very
costly. It is necessary to remark that the decomposition of the chloride of calcium is
already produced by the simple contact of this chloride with the neutral carbonate of
magnesia & even with the hydrated carbonate of this base the simultaneous
employment of the carbonic acid & of the carbonate of magnesia has especially for
its object to render the complete transformation rapid and economical.
D. The evaporation of the solution of chloride of magnesium to the degree of
concentration (el Mg + 17 Ho) is made in effecting this solution at the low
temperature of the worms in which, as already said, the hydrochloric acid is
condensed to the composition cl HI 16 HO. This evaporation is made without any
expense than that of the decomposition of the chloride of magnesium by heat.
E. The decomposition of chloride of magnesium into gascous hydrochloric acid and
into anhydrous magnesia such as already been industrially realised by Balard, is not
without inconvenience. It requires first that the chloride be concentrated to
44° Baumé in which case the whole becomes a hard mass on cooling, a mass that can
be broken in pieces, that one can introduce into a reverberatory furnace for to heat
them to a red heat. In operating thus the acid of the gases ought to be condensed by
means of cold water as is the practice in sulphate of soda works and through the
medium of masonry condensers of considerable dimensions as soon as important
quantities are begun to be acted upon. In this manner of operating these incon-
veniences are avoided among others that the evaporation of water is economized, that
the excess acid can be added not only to condense it but also to bring it to the state
of dilution necessary to make it act upon the phosphorite in view of the manufacture
of hydrated bicalcic phosphate.
Our entirely new method of operating is based on the fact that a concentrated
solution of hydrochloric acid submitted to the action of heat, evolves acid in the
gaseous state until the solution reaches the temperature of 110 degrees Centigrade.
From this moment, the acid is evolved combined only with 16 equivalents of water,
which it carries away with itself, whilst it distils without alteration at this temperature.
Consequently its condensation becomes possible without addition of water and gives
rise to a hydrated acid possessing a density of 1,094 corresponding to 13 degrees
of Beaume's areometer. In consequence the chloro-magnesian solution being in the
state (Cl Mg + 17 HO) is thrown in small portions and at sensibly equal intervals
of time (litre per second for instance) on the sole of a furnace heated to red heat;
this sole has the form of a circular basin with vertical rim 0'15 metres high, a flat
bottom 4 metres in diameter and is made of refractory clay. Under these conditions
a portion of this liquid being thrown on the sole, the solution water evaporates, then
the remainder (Cl Mg HO) is decomposed; the acid is evolved in the gaseous state
and the anhydrous magnesia is deposited on the sole. The same reaction taking place
with the next portion of liquid thrown on the sole, the water of this portion reduced
into steam meets the hydrochloric acid evolved from the previous portion, and as the
whole is led outside the furnace into a metallic worm dipping into a cooling liquid,
which is constantly renewed, the steam and the acid condense into a liquid, the
composition of which is (Cl H 16 HO). This liquid is collected as it comes out of the
worm, and is found to have just the degree of dilution required for the treatment of
phosphorite by hydrochloric acid. In operating thus, we are freed, first from the
evaporation of all the water, which it would be necessary to add to the acid for the
purpose of condensing it, as is usual in the manufacture of soda, and bring it after-
wards to show only a gravity corresponding to 13 degrees Beaumé ; second, from the
use of large and costly-condensers of masonry used by the soda manufacturers.
Lastly, we place ourselves in the best conditions to effect the decomposition of the
chloride of magnesium, for the magnesia in presence of the water steam with which

page_text: it is constantly in contact, could not take back acid, without the chloride resulting
therefrom, getting decomposed at once, by the action of this steam, into acid and
magnesia, and on the other hand, the chloride could not melt or frit and thus escape
the decomposing action of the water, only in so far as it could become anhydrous,
which is, however, not possible, in presence of the liquid which moistens it unceasingly,
and even dissolves it if need be.
If, before the introduction in the furnace, the evaporation of the chloro-magnesian
solution had been carried too far, which would be a fault, this could be remedied by
admitting into the decomposing furnace in a continuous manner, the portion of water
steam necessary to allow of the acid condensing itself in the state of Cl H 16 HO.
It is besides obvious that if we had to deal with chloride of magnesium, cooled into
a solid mass, and not containing the quantity of water required by the condensation
of an acid having a density of 1.094, it would be sufficient, in order to avoid the use of
masonry condensers, to introduce in the decomposition furnace, during the evolution
of the acid, enough water steam to obtain by condensation in worms, the acid having
a composition given by the formula (CI H. 16 HO). But this manner of operation
would be carrying us back entirely to the essence of our process, and for this reason,
it belongs naturally to it (see the vertical and horizontal section of the decomposing
furnace on the accompanying drawing).
As to
The magnesia resulting from the decomposition of the chloride of magnesium is
obtained in the anhydrous state. If it be desired to use it again in the manufacture
of the hydrated bicalcic phosphate, it is necessary to cause it to absorb an equivalent of
water to effect this it is boiled under a pressure of 2 or 3 atmospheres in a boiler.
ad hoc. Under these conditions, it becomes hydrated and fit for further use.
the part which would have resisted hydration (this being due to its having been
submitted to too high a temperature in the furnace) it is dissolved again in
hydrochloric acid, and is used in the charge of the next operation. Hydrated
magnesia, being a certain time in suspension in the liquid, from which it has borrowed
its hydrating water, is separated easily by simply decanting the liquid from the
magnesia, which has resisted hydration, and which precipitates easily. It is far
preferable to avoid the process of hydrating the anhydrous magnesia by borrowing
the hydrated magnesia from sea water, which gives it in this state, when it is treated
by slaked caustic lime and joining thus to the manufacture of hydrated bicalcic
phosphate that of magnesia extracted from the sea.
Under these conditions it is possible to supply the trade and industry with magnesia
at a comparatively low, but nevertheless very remunerative price, rendering it
accessible to all the industries which aspire to be able to utilise the valuable properties,
which magnesia possesses, namely, its absolute infusibility, its great water-proofness,
and its aptness to produce a ceramic paste both light and diaphanous. Phosphorite is
generally found on the sea coast or at comparatively short distances from the sea
coast, but even if it should be a few hundred kilometers from the coast, there would
be still a great advantage in transporting the magnesia extracted from the sea, to use
it in the manufacture of the hydrated bicalcic phosphate and thus make it an article
of commerce. This advantage is still greater in hot countries, and especially in the
neighbourhood of the salt marshes, where the chloride of magnesium becomes then not
only a source of magnesia, but also of hydrochloric acid, whilst in temperate regions
hydrochloric acid is returned to the sea in the form of chloride of calcium resulting
from the action of hydrated lime or sea water.
WM. P. THOMPSON & Co.,
6, Lord Street, Liverpool,
Filing Agents for the Applicant.

page_text: Improvements in the Method of and Apparatus for Manufacturing
Hydrated Phosphates and in Recovering Bye Products therefrom.
I, LOUIS GUSTAVE GHILAIN DAUDENART, of Brussels, in the Kingdom of Belgium,
Lieutenant General (retired) 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 :-
In the new mode of making phosphate which forms the subject of the present
invention, a new arrangement of gas generating furnace is employed, of which the
following is the Specification
In the drawings left with the provisional specification, the furnace is represented.
Figure 1 is a longitudinal section of the furnace on line A B of Figure 2.
Figure 2 is a section through the lines CD, EF, GH, of Figure 1.
Figure 3 is a section through the line IJ of Figure 1.
Figure 4 section through the line KL of Figure 1.
Figure 5 section through the line QR of Figure 1.
Figure 6 section through the line ST of Figure 1.
Figure 7 section through the line MN of Figure 2, and,
Figure 8 section through the line OP of Figure 2.
a is the gas generator. entrance of the combustible gases into the circular
distribution flue. e circular distribution flue of combustible gases. d walls separating
the flue e from the flue e, where the combustible gases are brought to encounter the
air in Q, and to he inflamed. entrance of the air into the furnace.
g circular
distribution flue for the air. walls separating the flue from the circular flue i,
where the air arrives to exit at j, and to mix in 7 with the combustible gases which it
ignites. large arched flue giving to the exterior air a second entrance into the
furnace. arched space conducting the air into the circular flue m. m² circular
distribution flue for air entering at o. n walls separating the flue m' from the circular
flue o where the air enters to go out at p, and to mix in with the combustible gases
which it inflames. metallic sole formed of plates of cast iron. It is upon this sole
that the chloride of magnesium arrived at the desired degree of concentration, is
projected in the form of liquid dust, in order to be decomposed and to produce
hydrochloric acid. This latter, distilling with the vapour of water is condensed by
refrigeration, by means of a worm where it exits, combined with water-at-the density
of 1.094. s arches or bridges. of refractory-bricks upon which are supported cast
iron bars, destined to transmit the heat to the plates of cast iron constituting the sole,
and to prevent the direct contact of these plates with the flame.. The metallic sole
q

page_text: can be replaced if necessary, by a sole of refractory bricks. t circular wall serving
also as a support to the plates of cast iron, or to the refractory bricks. u central exit
flue of the burnt air. flue for causing the hot gas to circulate under that part of
the sole not heated directly. w. flue conducting the hot gases under the roof b', and
thence to the chimney. opening for urging the draught of the fire of the gas
generator. y grate for supporting the fuel.. movable valve for forming an outlet
for the air dilated by the instantaneous combustion of the combustible gases at the
time of lighting. a¹ exit of gas produced by the decomposition of the chloride of
magnesium which goes off to the condensor. 61 roof receiving the chloride of
magnesium arrived at the degree of concentration, and coming from the evaporating
apparatus.
N. The letters above are shown as far as necessary upon the Figures 1 to 8, which
Figures describe all the furnace for the decomposition of chloride of magnesium.
Whatever be the composition of the phosphate to be treated, it is submitted first of
all to a cold washing in ordinary water, which has for its object to take up the soluble
particles in the water, and to separate at the same time by decantation, the insoluble
parts of little density, (ochreous clay, carbonate of lime, called in French, "folle
farine, silica, sand, etcetera) which can be removed without taking with them
phosphate. This operation terminated, there remains a composition essentially formed
of tricalcic phosphate of carbonate of lime combined with phosphate or not, of silica,
of sand, various insoluble matters, which taken all together may be considered as a
first product, which will be called hereafter Ph. L, and which I call "phosphorite
lavée" (washed phosphorite).
The process of making hydrated bicalcic phosphate comprises the following
operations, based upon the chemical reactions which are given hereafter in the form
of formulae.
A. Treatment of the first product by dilute hydrochloric acid giving a solution
principally formed of chloride of calcium, and acid phosphate of lime.
PO' CaO+n (C) — o² C — a O) + L
matters, etcetera) + (n + 2) {CI H, 16 HO}
(n + 2) 16 HỌ + n (HỌ) + n COA + Lạ.
(silica, sand, matters inert in soluble
(Po' Ca O 2 HO) + (n + 2) Cl Ca +
B. Treatment of the hydrochloric solution of phosphorite by hydrated magnesia,
and sanaration of the main
2, (Po' Ca O 2 HO) + 2 (n + 2) cl Ca + 2 (n + 2) 16 HO + 2 n (HO) + 2
(Mg O HO) = 2 (PO 2 Ca O HO) + 2 (cl Mg) + (2n + 2) el Ca + 2 (n + 2)
C. Treatment of the resulting neutral solution principally formed of chloride of
calcium, and of chloride of magnesium by neutral carbonate of magnesia, and of
carbonic acid, until complete transformation of the chloride of calcium into dissolved
chloride of magnesium, and into insoluble carbonate of lime which are separated from
each other.
(cl Mg) + (2n + 2) cl Ca + 2 (n + 2) 17 HO + (2n + 2) Co² Mg 0 +
(2n+2) Co² 2 (n + 2) cl Mg + (2 n + 2) Co² Ca 0+ (2n + 2) Co² + 2 (n+2)
ITC

page_text: E. Decomposition by heat of the hydrated chloride of magnesium into hydrochloric
acid for one part, and into anhydrous magnesia for the other part, then condensation
of the acid in the state of C1 I, 16 HO.
2 (n+2) cl Mg + 2 (n + 2) 17 HO =2 (+2) (el H 16 HO) + 2 (n + 2)
M. Ò.
The aforesaid operations will be now passed in review, under the heads A, B, C,
D, E.
A. The first operation is effected by means of dilute hydrochloric acid. It is
employed at the density of about 1.094, marking about 13 degrees on the areometer
of Baumé, and having the composition of CI H, 16 HO. All the acid employed ought
to be converted into chloride of calcium, and the phosphate into acid phosphate of
lime. To obtain this result, there ought to be an excess of the first product, and the
process ought to be stopped when a portion of the liquor filtered and treated by a
drop of ammonia in solution, gives a precipitate which will not dissolve by further
agitation of the liquor.
B. The second operation consists in adding to the solution of phosphorite, hydrated
magnesia newly precipitated and perfectly divided, until complete nentralisation, that
is to say, until the liquor no longer alters blue litmus paper (papier bleu de tournesol)
and is no longer alkaline. The liydrated magnesia presents over hydrated lime this in-
portant advantage, that with magnesia, a neutral phosphate of hydrated magnesia
(Po³ 2 Mg O HO) is first formed, which is soluble in water and which consequently,
can only give with the choloride of calcium in solution in the water, bicalcic hydrated
phosphate, whilst with lime a tricalcic phosphate is often formed, which diminishes
thus the mercantile value of the precipitate, which with a view to constitute an
immediately assimilable manure, ought to present itself under the form of hydrated
bicalcic phosphate.
It is important further to remark that although the precipitation by lime is publicly
known, the entire set as a whole of the chemical reactions which constitute this process
over the manufacture of precipitated phosphate, and all the revivification of the
reagents employed, is believed to be new, and that whether lime or magnesia be used
as a precipitating agent.
C. The complete transformation of chloride of calcium into chloride of magnesium,
and into carbonate of lime is obtained by means of carbonate of magnesia acting under
pressure with an excess of carbonic acid. It is generally known that in order to
produce carbonates under pressure it is necessary to use pure carbonic acid, the
effect of the pressure becoming insignificant when this acid is mixed with a strong
preparation of inert gases, such as those which are obtained by the combustion of
coals in industrial furnaces. Therefore, if one operates upon the magnesia in
suspension in a solution of chloride of calcium, the quantity of pure carbonic acid
acting under pressure, becomes considerable, since to act completely upon the chloride
of calcium, all the corresponding magnesia ought to be transformed into carbonate.
The result is a great loss of time besides a great expenditure of pure carbonic acid.
To avoid this double inconvenience, the hydrate of magnesia is transformed first into
neutral carbonate of magnesia, and this by exposing it to the action of the gases
resulting from the combustion of coal in industrial furnaces, gas generators, or others,
or even to the action of carbonic acid, which has been mixed with gases not powerful
to prevent its action, or to destroy it. The carbonic acid under pressure of two or
three atmospheres is made to react upon carbonate of magnesia, in suspension in a
solution of chloride of calcium. In these conditions the carbonetation of the lime
takes place rapidly, and the quantity of carbonic acid employed is at a minimum, all
the more that the pure carbonic acid which has eventually traversed the liquid without
being absorbed, returns to the gasometer to be extracted anew from it, and employed
again without causing the least interruption in the work of the gas pump employed
for this purpose.

page_text: This new manner of proceeding, admits at the same time of great economy of time
and of money, the production of the pure carbonic acid being relatively very costly.
It is necessary to remark that the decomposition of the chloride of calcium, is already
produced by the simple contact of this chloride with the neutral carbonate of magnesia,
and even with the hydrated carbonate of this base. The simultaneous employment of
carbonic acid and of carbonate of magnesia has especially for its object to render the
complete transformation rapid and economical.
D. The evaporation of the solution of chloride of magnesium to the degree of
concentration Cl Mg +17 HO, is effected by utilising said solution for cooling the
worms in which, as will be explained below, the hydrochloric acid is condensed to the
composition Cl H 16 HO.
This evaporation is made without any expense than that of the decomposition of
the chloride of magnesium by heat.
E. The decomposition of chloride of magnesium into gaseous hydrochloric acid,
and into anhydrous magnesia, such as has already been industrially realised by Balard
is not without inconvenience. It requires first, that the chloride be concentrated to
44 degrees Baumé, in which case the whole becomes a hard mass on cooling, a mass
that must be broken in pieces, which are introduced into a reverberatory furnace for
the purpose of heating them to a dark red heat. In operating thus, the acid of the
gases ought to be condensed by means of cold water, as is the practice in sulphate of
soda works, and through the medium of masonry condensers of considerable dimensions
as soon as important quantities have to be acted upon. In this manner of operating,
these inconveniences are avoided besides the economy resulting from the evaporation
of the water, which must be added to the gaseous acid, not only for the purpose of
condensing it, but also for that of bringing it to the state of dilution necessary to
make it act on the phosphorite, with a view to manufacturing hydrated bicalcic
phosphate.
This entirely new method of operating is based on the fact that a concentrated
solution of hydrochloric acid submitted to the action of heat, evolves acid in the
gaseous state, until the solution reaches the temperature of 110 degrees Centigrade.
From this moment, the acid is only evolved combined with 16 equivalents of water,
which it carries away with itself, whilst it distils without alteration at this temperature.
Consequently its condensation becomes possible without addition of water and gives
rise to a hydrated acid possessing a density of 1.094 corresponding to 13 degrees of
Baume's arcometer. In consequence the chloro-magnesian solution being in the state
(CI Mg+17 HO) is thrown in small portions and at sensible equal intervals of time
(litre per second for instance) on the soles of a furnace heated to red heat this sole
has the form of a circular basin with vertical rim 0.15 mètres high, a flat bottom
4 mètres in diameter, and is made of refractory clay. Under these conditions, a
portion of this liquid being thrown on the sole, the solution water evaporates, then the
remainder (Cl Mg HO) is decomposed; the acid is evolved in the gaseous state, and
the anhydrous magnesia is deposited on the sole. The same reaction taking place
with the next portion of liquid thrown on the sole, the water of this portion formed
into steam meets the hydrochloric acid evolved from the previous portion, and as the
whole is led outside the furnace into a metallic worm dipping into a cooling liquid,
which is constantly. renewed,. the steam and the acid condense into a liquid, the
composition of which is (Cl H 16 HO.). This liquid is collected as it comes out of
the worm, and is found to have just the degree of dilution required for the treatment
of phosphorite by hydrochloric acid. By operating thus, the following disadvantages
are avoided: First, the evaporation of all the water, (which it would be necessary to
add to the acid) for the purpose of condensing it, as is usual in the manufacture of
sulphate of soda, and bringing it afterwards to show only a gravity corresponding to
13 degrees Baumé ; Second, the use of large and costly condensers of masonry, used
by the soda industry. In short, the best conditions to effect the decomposition of the
chloride of magnesium are secured, for the magnesia in presence of the vapour of
water with which it is constantly in contact, cannot combine with the acid, without
the chloride resulting therefrom getting decomposed at once, by the action of this
P

page_text: steam, into acid and magnesia; and on the other hand, the chloride could not melt
nor frit, and thus escape the decomposing action of the water, except by becoming
anhydrous; this is, however, impossible as the chloride is in presence of the liquid
which moistens it unceasingly, and even dissolves it if need be.
If, previous to the introduction in the furnace, the evaporation of the chloro-
magnesian solution had been carried too far, (which would be a fault), this could be
remedied by admitting into the decomposing furnace in a continuous manner, the
portion of vapour of water necessary to allow of the acid condensing itself in the state
of Cl H 16 HO.
It is besides obvious, that if one had to deal with chloride of magnesium, cooled into
a solid mass, and not containing the quantity of water required by the condensation
of acid having a density of 1.094, it would be sufficient, in order to avoid the use of
masonry condensers, to introduce in the decomposition furnace, during the evolution of
the acid, enough vapour of water to obtain by condensation in worms, the acid having
a composition given by the formula (Cl H. 16 HO). But this manner of operating
would be carrying us back entirely to the essence of the new process, and for this
reason it belongs naturally to it, (for.details see the vertical and horizontal sections of
the decomposing furnace on the accompanying drawing).
The magnesia, resulting from the decomposition of the chloride of magnesium, is
obtained in the anhydrous state. If it be desired to use it again in the manufacture
of the hydrated bicalcic phosphate, it is necessary to cause it to absorb one equivalent
of water; to effect, this it is boiled under a pressure of 2 or 3 atmospheres in a
boiler ad hoc. Under these conditions, it becomes hydrated and fit for further use.
As to the part which would have resisted hydration (this being due to its having been
submitted to too high a temperature in the furnace) it is dissolved again in hydro-
chloric acid, and is used in the charge of the next operation. Hydrated magnesia, as it
remains a certain time in suspension in the liquid, from which it has borrowed its
hydrating water, is separated easily by simply decanting the liquid from the magnesia,
which has resisted hydration, and which precipitates easily. It is far preferable to
avoid the process of hydrating the anhydrous magnesia by borrowing the hydrated
magnesia from sea water, which gives it in this state, when it is treated by slaked
caustic lime, and joining thus to the manufacture of hydrated bicalcic phosphate that
of magnesia extracted from the sea.
Under these conditions it is possible to supply the trade and industry with magnesia
at a comparatively low, but nevertheless very remunerative price, rendering it
accessible to all the industries, which aspire to be able to utilise the valuable properties,
which magnesia possesses, namely, its absolute infusibility, its great water-proofness,
and its aptness to produce a ceramic paste both light and diaphanous. Phosphorite is
generally found on the sea coast, or at comparatively short distances from the sea
coast, but even if it should be a few hundred kilometers from the coast, there would
be still a great advantage in transporting the magnesia extracted from the sea, to use
it in the manufacture of the hydrated bicalcic phosphate, and thus make it an article
of commerce. This advantage is still greater in hot countries, and especially in the
neighbourhood of the salt marshes, where the chloride of magnesium becomes then
not only a source of magnesia, but also of hydrochloric acid, whilst in temperate
rogions, hydrochloric acid is returned to the sea in the form of chloride of calcium,
resulting from the action of hydrated lime or sea water.
Having now particularly described and, ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what
1 claim is:-
1. The application and arrangement of the chemical reactions herein before set forth,
under heads A B C D and E (and this independently of the apparatus capable of
realising them) to the manufacture of hydrated bicalcic phosphate called "precipitated
phosphate," and to the revivification of the hydrochloric acid, and of the magnesia
employed as reagent in this process of manufacture, substantially as described.

page_text: 2. The employment of hydrated magnesia, for the neutralisation of the hydro-
loric solution of phosphorite, and the simultaneous precipitation of hydrated bicalcic
osphate, substantially as described.
3. The employment of neutral carbonate of magnesia, or of its hydrocarbonate, for
e transformation with or without pressure, by means of carbonic acid or not, of
e chloride of calcium into chloride of magnesium, and into carbonate of lime,
bstantially as set forth.
4. The method of industrial manufacture herein described, of hydrochloric acid, by
eans of hydrated chloride of magnesium, which method of manufacture is characterised
the following facts:
(a). That the acid thus produced does not separate itself from its water of com-
bination that it has the composition (Cl H 16 HO) and that it distils
without alteration at the temperature of 100 degrees Centigrade;
(4). That in order to produce it, the solution of chloride of magnesium having the
composition C Mg + 17 HO, must be thrown in small successive portions, and
at sensibly equal intervals of time, (tolitre per second for example), on a
sole preferably made of refractory bricks, and heated to a red heat so as to
produce an alternating evolution of hydrochloric acid, and of water steam;
that the acid and water steam are then condensed in a special apparatus
entirely differing from those used at present, for the condensation of com-
mercial hydrochloric acid, that is to say, by means of worms made of a metal
that is a good conductor of heat (copper for instance), and cooled constantly
by a liquid which is constantly renewed and more especially a diluted solution
of chloride of magnesium, said industrial method of condensation constituting
a new process, in that which concerns more especially hydrochloric acid.
5. The furnace for the decomposition of the hydrated chloride of magnesium hy
at, substantially as herein described.
6. The use of steam, superheated or at a pressure higher than the atmospheric
essure, for the purpose of producing rapidly the hydration of anhydrous magnesia,
bstantially as described.
7. The simultaneous employment of sea water, or of chloride of magnesium, what-
er its origin may be, with hydrated lime for the purpose of producing in a continuous
anner hydrated magnesia, and in a more general manner anhydrous magnesia, and
drochloric acid, by the action of heat in the above mentioned furnace.
Dated this 9th day of August 1888
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Filing Agents for the Applicant.