IMPROVEMENTS IN PRECIPITATING CERTAIN SALTS
Year: 1855

page_text: LETTERS PATENT to Louis Joseph Frédéric Margueritte, Chemist, of
Paris, in the Empire of France, for the Invention of "IMPROVEMENTS IN
PRECIPITATING CERTAIN SALTS."
Sealed the 23rd May 1856, and dated the 26th November 1855.
PROVISIONAL SPECIFICATION left by the said Louis Joseph Frédéric
Margueritte at the Office of the Commissioners of Patents, with his
Petition, on the 26th November 1855.
I, LOUIS JOSEPH FRÉDÉRIC MARGUERITTE, Chemist, of Paris, in the Empire
of France, do hereby declare the nature of the said Invention for IMPROVE-
MENTS IN PRECIPITATING CERTAIN SALTS, to be as follows:-
My Invention relates to the property possessed by certain substances of
precipitating by dissolution several salts, such as chlorides of potassium, of
sodiumi, of ammonium, of barium, of carbonate of soda, of ferrocyanate of potas-
sium, &c. &c. Thus, for example, by introducing until saturation a current
of chlorhydric acid gas into a dissolution containing chloride of potassium or
of sodium, those two salts are almost entirely separated from the liquid.
Chlorhydric acid gas, having a close affinity with water, deprives the salt of
its dissolving agent, and thus makes it settle in a solid. state. This means
renders it unnecessary to evaporate the saline dissolutions, but it is useless to
compare it here to the common evaporating processes, which are very simple,

page_text: and not very expensive; its aim is quite peculiar, and the result obtained could
not be arrived at otherwise.
It is well known that in order to prepare the white salt used for dinner
tables (chloride of sodium), rough salt is required to be refined by making it
undergo successive dissolutions and crystallizations, in order to take away from
it strange and deliquescent salts, and, finally, to have its last dissolution
undergo a very slow evaporation, in order that the salt which settles should
become finest and most divided.
The salt which has been prepared by chlorhydric acid is to be found imme-
diately, because that acid does not precipitate in the same circumstances the
deliquescent salts with which it might be impregnated, amongst others, chloride
of magnesium.
The following is the way of operating:-A dissolution of common salt is
made, into which a current of chlorhydric acid gas is introduced; every
bubble of gas produces an agitation through the salt which precipitates, and
that agitation continues until the liquid is saturated with chlorhydric acid
and has given off all its salt. The salt is made to drip as much as possible,
after which it is spread on an oven or stove conveniently heated, by which
means it is freed from the chlorhydric acid that impregnates it without
retaining the least trace of it. When the salt has thus been completely dried,
it is perfectly pure and of a remarkable whiteness, which doubtless originates
in the mass being formed of a multitude of extremely small, similar, and very
brilliant crystals, which gives it a silky aspect.
Chloride of potassium is, precipitated by chlorhydric acid with the same
facility as sea salt, which permits its being extracted from mother waters, from
salt marshes, and also its being separated from chloride of magnesium and
sulphate of magnesia, which are not, as has been already said, precipitated in
these circumstances by a current of chlorhydric acid; therefore, instead of
crystallizing the bichloride of potassium and magnesium, which must be re-
dissolved in order to separate the chloride of potassium, it is merely required
for obtaining immediately the latter salt to cause chlorydric acid gas to pass in
the mother waters without submitting them to evaporation.
The insolubility of chlorides of potassium and sodium in chlorhydric acid is
so great as to make them precipitate whenever they pre-exist or may be formed
in a dissolution. Thus, the sulphates of soda & potash, and generally all
soluble salts of those two bases, allow chloride of sodium or potassium to settle
under the influence of chlorhydric acid. In this reaction the chlorhydric acid
begins by transforming a part of the sulphate into chloride, which it causes
afterwards to settle by insolubility, the liquid retaining a corresponding quantity

page_text: of eliminated sulphuric acid, which may be withdrawn by distillation.. Those
facts may explain how it happens that in passing chlorhydric acid gas into the
concentrated water of the Mediterranean, almost all, the soda and potash are
precipitated in the state of chlorides, although part of those alkalis are in the
state of sulphates. The bisulphate of potash and magnesia, when submitted to
the action of chlorhydric acid, leaves thus its potash in the state of insoluble.
chloride.
The above-described operation, which consists in introducing a current of
chlorhydric gas into the dissolution of chloride of potassium or sodium, and
their sulphates, in drying in an oven or stove the precipitate obtained thereby,
is very simple, and does not present any practical difficulty; but the advan-
tages it may offer depend entirely upon the facility or economy of obtaining
chlorhydric acid.
Now, in all soda works considerable quantities of chlorhydric acid aré
obtained through the decomposition of sea salt; it will therefore be very
easy to direct the acid gas into condensing recipients filled with water
saturated with sea salt, or the salt of potash or soda about to be treated; tho
precipitated salt will be obtained, and the chlorhydric dissolution will not have
lost its value as an acid, and may be employed for its common uses chiefly for
the preparation of chloride of lime. In case the operation could not go on
near some sóda works, the same chlorhydric acid might serve almost indefi-
nitely. This is effected by disposing two recipients communicating by a tube;
the first containing chlorhydric acid, and a certain quantity of rough chloride
of sodium, whose function will be determined hereafter; the second contains
the saline dissolution about to be precipitated.
By heating the first recipient, the chlorhydric gas is freed and dissolved in
the saline dissolutions of the second recipient, which by degrees will settle all
its salt. However, it is well known that by boiling a dissolution of chlorhydric
acid the greater part of the gas is freed, but that at a certain degree the
combination between the water and the gas is no longer destroyed by heat,
and thus a distillation of chlorhydric acid greatly diluted is produced. If that
diluted acid went from the first recipient into the second the effect and end of
the concentration would not be attained; therefore the chlorhydric dissolution
receives additional rough salt, which by dissolving diminishes the mutual
affinity between the water and the acid, and removes finally the latter under
the influence of heat. The salt thus added in the first recipient has for its
end, 1°, to remove the chlorhydric gas; 2°, to produce the saline dissolution,
which is likewise to be precipitated. By the alternately heating & the
reciprocal operation of those two apparatus, it is evident that the water loses

page_text: its acid whilst the other absorbs it, and that on one part the salt settles whilst
on the other it dissolves; in other words, that the two recipients are alter-
nating their functions. The only interruption that exists in the continuous
operation is that which unavoidably results from the separation of the acid
liquid from the precipitated salt, which is simply effected by decantation in a
separate vessel.
I shall finally mention another application of that principle of insolubility.
It consists in bathing chlorides of potassium and sodium in concentrated chlor-
hydric acid, which takes away from them the strange and deliquescent salts.
Thus, the bichloride of potassium and magnesium when bathed in chlorhydric
acid is decomposed in two, and and separated completely from the chloride of
magnesium, which dissolves and is taken off in the acid liquid. It is easily to
be understood that the precipitation and bathing of the chlorides are one and
the same thing, since the sea salt precipitates from its dissolution or may be
bathed without dissolving by means of the chlorhydric acid, it being insoluble
in that acid.
The agent that is employed for the precipitation must of course vary,
according to the nature of the salts to be precipitated. Those that may be
decomposed by the chlorhydric acid, as, for example, the carbonate of soda,
cannot be precipitated by it; but there exists another agent, which, like the
chlorhydric acid, is very soluble in water and volatile, which is the ammoniac
gas. By introducing until saturation ammoniac gas into a dissolution of
carbonate of soda, that salt settles in a crystalline and anhydrous state. Thus,
by operating on a dissolution of rough soda a very pure carbonate of soda is
obtained, since the other salts that accompany it are not precipitated by the
ammoniac gas. Such are the sea salt, the sulphate of soda, the sulphite of
sodium, the caustic soda. For obtaining carbonate of soda from rough soda
a more simple way of operating may be adopted, viz., by means of bathing, as
with the chlorhydric acid. The rough soda is reduced into a fine powder, on
which is filtered a dissolution saturated with ammonia; all strange substances
are dissolved, and the carbonate of soda is left in a pure state after having
been dried. It may be added, that the mode of operation with ammonia is
the same as with chlorhydric acid, viz., in reciprocal apparatus, and that the
same quantity of volatile alcali is employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Louis Joseph Frédéric Margueritte in the Great Seal
Patent Office on the 26th May 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, LOUIS
JOSEPH FREDERIC MARGUERITTE, Chemist, of Paris, in the Empire of France,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-sixth day of November, in the year of our
Lord One thousand eight hundred and fifty-five, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me. the
said Louis Joseph Frédéric Margueritte, Her special licence that I, the said
Louis Joseph Frédéric Margueritte, my executors, administrators, and assigns,
or such others as I, the said Louis Joseph Frédéric Margueritte, my excci-
tors, 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 "IMPROVEMENTS IN PRECIPITATING CERTAIN SALTS," upon the
condition (amongst others) that I, the said Louis Joseph Frédéric Margueritte,
by an instrument in writing under my hand and seal, 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 Louis Joseph Frédéric Margueritte,:
do hereby declare the nature of my said Invention, and in what manner the:
same is to be performed, to be particularly described and ascertained in and
by the following statement:-
This Invention relates to that property which certain substances have of
precipitating from their dissolution various salts, such as the chlorides of
potassium, sodium, ammonia, barium, the carbonate of sodium, the cyano-.
ferrure of potassium, &^. If, for instance, a current.of chlorhydric acid gas is.
let to a full saturation into a dissolution consisting of chlorides of potassium
and of sodium, these two salts will be almost entirely eliminated from the
liquid. The chlorhydric acid gas, which is most congenial to water, will take
from it its dissolvent, and settle it in the solid state. By this means the vapo-
rizing of the saline substances will be dispensed with; but I do not intend
comparing my process to the common vaporizing. processes, which are very

page_text: plain and unexpensive, its intent being quite special, and no result being likely
to be obtained by any other means.
It is well known that for obtaining table salt or chloride of sodium, raw salt
is to be refined, by being submitted to various dissolutions and successive cristal-
lizations, in order to purge it of all extraneous deliquescent salts, and, finally,
the last dissolution is to be very slowly vaporized, that the settled salt may be as
fine as possible. The salt obtained by means of chlorhydric acid is instantly
purified, as this acid does not precipitate, in the like circumstances, the
deliquescent salt it may contain, such as the chloride of magnesium.
.
I shall now describe the manner in which my Invention is carried into
eflect. A dissolution of common salt is made, into which I let a current of
chlorhydric acid gas, each bubble of which will occasion an agitation as the
salt precipitates, and this agitation will continue until the liquid is saturated
with chlorhydric acid and has lost all its salt. The salt is then drained and
spread on the sole of an oven or stove room, suitably heated, where it lets off
entirely the chlorhydric acid with which it is impregnated.
Thus, being completely dryed, the salt is remarkably pure and nice, as it
chiefly consists of an indefinite number of glittering silky atom-like crystals.
Chloride of potassium is precipitated by chlorhydric acid as easily as marine
salt, which allows extracting it from the mother waters of salt marshes and
separating it from the chloride of magnesium: and the sulphate of magnesia,
which are not, as has been said, precipitated in the like circumstances by a
current of chlorbydric acid; consequently, instead of crystallizing the double
chloride of potassium and of magnesium, which is to be dissolved again that
- the chloride of potassium may be insulated, it will suffice for obtaining the last
salt to let into the mother waters a current of chlorhydric acid gas without
submitting them to evaporation.
The insolubility of the chlorides of sodium and of potassium in the chlor-
hydric acid is such, that those salts will be precipitated whether they are pre-
existing or liable to be formed in a dissolution.
Thus, the sulphates of soda and of potash, and generally all soluble salts of
these two bases, allow the chlorides of sodium and of potassium to settle under
the influence of chlorhydric acid. In this reaction the chlorhydric acid first
transforms a part of the sulphate into chloride, which it afterwards causes to
settle, as being insoluble, and there now remains in the liquid a corresponding
quantity of sulphuric acid that is eliminated, and may be removed by distilla-
tion. From this it appears, that when letting chlorhydric acid gas into the
concentrated waters of the Mediterranean sea, the whole quantity of soda and
of potash is precipitated in the state of chlorides, though a part of these alkalis.

page_text: is found in the state of sulphates. The double sulphate of potash and of
magnesia being submitted to the action of chlorhydric acid, lets off its potash.in
the state of insoluble chloride.
The process I have just described, which consists in letting a current
of chlorhydric acid gas into a dissolution of chlorides of potassium and of
sodium, and also of their sulphates, and drying in an oven or stove room the
precipitate obtained, is very plain, and practically can meet with no difficulty;
but the advantages it yields are merely depending on the facility of getting the
chlorhydric acid, and the cheapness at which it is obtained.
In all soda works considerable quantities of chlorhydric acid are collected,
which result from the decomposition of marine salt by SO 3; it is very easy to.
convoy the said acid gas into condensing recipients filled with water saturated
with marine potash or soda salt; the precipitated salt will thus be obtained,
the chlorhydric dissolution will not be deprived of its commercial value, and
may be used for usual purposes, specially for preparing chloride of calcium
(lime). Were not the operation annexed to some soda works, the same chlor:
hydric acid may be made use of almost indefinitely. To this end, two recipients
are set in communication through a tube; the former including, chlorhydric
acid as found in trade, and a quantity of raw chloride of sodium, the use of
which I shall describe hereafter, and the latter recipient including the salt
dissolution that is to be precipitated.
By heating the former recipient, the chlorhydric gas will evolve and come
to dissolve itself into the salt dissolution contained in the latter, where all its
salt will gradually settle. It is well known, however, that by ebullition most
part of the gas will evolve from the dissolution; but there is a certain boiling
point when the combination between water and gas can no longer be broken
by heat, and when a distillation of chlorhydric acid very diluted takes place;
should the said acid thus diluted pass from the former recipient into the latter,
the effect and purpose of the concentration should not be attained. To the
chlorhydric dissolution I add some raw salt, which dissolving, diminishes tho
mutual affinity of water and the acid, and at last displaces the latter under
the influence of heat. This addition of salt in the former recipient will answer
a double purpose; it removes first the chlorhydric acid, and at the same time
works the salt dissolution that is to be precipitated in its turn. From the
alternate heating and reciprocal working of the two apparatus, it appears that
one lets off its acid whilst the other absorbs it, and that the salt settles in one
and is dissolved in the other, that, in a word, each recipient plays an alternate
part. The only interruption in the continuity of the working is that which
results of course from the separating of the acid liquid from the precipitated
.

page_text: salt, which is plainly effected by decanting it into a separate vessel. These
details will prove sufficient to impart a full idea of the process; but I shall givo
a last instance or application of this principle of insolubility, which consists in
dipping the chlorides of potassium and of sodium into concentrated chlorhydric
acid, thereby the extraneous and deliquescent salts are washed off, and the
double chloride of potassium and of magnesium thus purified is divided, and
lets off the chloride of magnesium, which being dissolved, is carried away into
the acid liquid. It is evident that the precipitation and washing of chlorides
are the same, for marine salt either precipitates from its dissolution, or may be
washed without being dissolved by means of chlorhydric acid, the said salt
being insoluble in this acid.
The passage of chlorhydric acid gas through the liquid may give rise to
some obstructions. which are easily set right by means of a rod, so adjusted in
the tube as to be capable of moving from upwards to downwards (see the
accompanying Drawing, Fig. 1). But instead of the muddling process, the
chlorhydric acid gas may be brought up to the surface of the liquid by means
of two plates hung in the same manner as common scales, which being
alternately immersed are to keep the liquid in a state of continual agitation,
as shewn in the accompanying Drawing, Fig. 2, in which A shows the coming
up of the gas; B, the coming up and level of salt water; C, C, the plates or
scales; D, E, D, the beam; F, the fulcrum; K, K, the stuffing box for the
rods; N, the level of the saline settling, and also of the efflux of the liquid
acid. Salt water is made to come through the tube B into the stone trough,.
and there to lie level to B.
.
:
Chlorhydric acid gas is evolved through the tubo A; the plates C, C, are
operated by any suitable power, and being. immersed alternately into the
liquid, keep the surface of the same in a state of constant. agitation. The
absorption of chlorhydric acid into salt water causes the salt to precipitate,
and upon full saturation of the liquid the working of the plates or scales is
stopped, and the marine salt is permitted to settle, lying level to the orifice N,
through which the acid dissolution is made to flow. out, being then made up at
B by a fresh supply of salt water.
. The settling of the salt being once effected, the lid P is lifted, and the salt
collected by means of a shovel, which may be similar to that used for
extracting river sand. The salt is afterwards taken to the stove rooin, where
it is completely cleared of the chlorhydric acid it may still contain.
The means which constitutes a characteristic part of my Invention is yet
grounded on another property. It is well known that a salt dissolution being
saturated by ebullition will on cooling, yield but an unimportant. quantity of

page_text: salt, for marine salt is not much more soluble in the warm than in the cold
state; but if, instead of neat or pure water, diluted chlorhydric acid is used,
the salt will begin to dissolve under the influence of heat, and then be
precipitated by cooling, thereby the precipitating power of chlorhydric acid
being restored.
I may use, for instance, chlorhydric acid diluted with sixteen equivalents
of water (Cl. 16 H O), marking out 12° Beaumé, of 1.09 density, and
containing 18 18 per cent. of gaseous acid, and have it boil on a predominant
quantity of marine salt. I decant afterwards the hot liquid, and stir it while
cooling; an atom-like salt will precipitate therefrom, which is separated from
the liquid and then dryed in the stove room.
The acid liquor, the mother water, is again made to boil on salt, and may
be used indefinitely for successive dissolutions and precipitations. The mother
water after a complete cooling will yet contain some. salt, but, once:dissolved,
this quantity still keeps the same for all further operations.
I wish it to be understood that the density that I have determined 'for the
dissolving water is not exactly positive, but may be more or less without
prejudicing the operation in the least. However, the quantities of dissolved
precipitated salt may vary in proportion of the said density.
The agent employed for the precipitation will necessarily vary according to
the nature of the salts to precipitate; such as are decomposable by chlor-
hydric acid, the carbonate of soda, for instance, cannot be precipitated by it.
But there is another agent that is, like chlorhydric acid, very soluble in
water and volatile, ammoniacal gas. If a quantity of ammoniacal gas is let,
till perfect saturation, into a dissolution of carbonate of soda, this salt will be
precipitated in the crystalline anhydrous state. When operating, for instance,
on a dissolution of raw soda, carbonate of soda will be obtained sensibly
purified, for the other salts that accompany it are not precipitated by, ammo-
niacal gas. These are marine salt, sulphate of soda, sulphuret of sodium,
caustic soda. The extraction from raw soda of the carbonate of soda may be
effected in a still plainer manner, that is, by the washing process, as is done
with chlorhydric acid; raw soda is reduced to a fine powder, upon which
a dissolution saturated with ammonia is poured, thereby the extraneous
substances are dissolved, and the carbonate of soda remains very sensibly
purified when dryed.
It is almost needless to add, that with ammonia, as with chlorhydric acid,
the same reciprocal apparatus and the same proportions of volatile alkali are
used.
:
Having thus described the nature of my Invention, and the manner in which

page_text: the same is or may be carried into effect, I wish it to be distinctly understood
that I do not confine myself to the precise details herein described, as such
may be varied or modified without departing froni the principle of action
thereof; likewise I do not confine myself to the strict figure or form of the
apparatus or portions of the apparatus herein described; but what I claim as
novel, and therefore being secured to me by the herein-before in part recited
Letters Patent, is,―
First, the precipitation by chlorhydric acid of marine salt in a pure white
divided state, whether I use the acid from soda works or I employ the same
in what I have termed reciprocal apparatus.
Second, the precipitation by chlorhydric acid of the chlorides of sodium and
of potassium from a dissolution of sulphate of soda or of potash of any
source, which allows the collecting of sulphuric acid and the precipitation of
the chloride of sodium from the dissolution of double chloride of potassium
and of magnesium.
Third, the purification or washing by chlorhydric acid of the chlorides of
potassium and of sodium.
Fourth, the use of chlorhydric acid diluted for dissolving in the warın state
marine salt and precipitating it atom-like in, the cold state by nierely stirring
or agitating the liquid.
Fifth, the precipitation of carbonate of soda by aminoniacal gas, and the
purifying of raw soda by washing it into a dissolution saturated with
ammonia.
In witness whereof, I, the said Louis Joseph Frédéric Margueritte, have
hereunto set my hand and seal, this 25 day of May, in the year of
our Lord One thousand eight hundred and fifty-six.
L. J. F. MARGUERITE. (L.S.)