IMPROVEMENTS IN PURIFYING ROCK AND SEA SALT
Year: 1856

page_text: LETTERS PATENT to Louis Joseph Frédéric Margueritte, of Paris, in the
Empire of France, Chemist, for the Invention of "IMPROVEMENTS IN
PURIFYING ROCK AND SEA SALT."
Scaled the 17th April 1857, and dated the 11th December 1856.
PROVISIONAL SPECIFICATION left by the said Louis Joseph Frédéric
Margueritte at the Office of the Commissioners of Patents, with his
Petition, on the 11th December 1856.
I, LOUIS JOSEPH FREDERIC MARGUERITTE, of Paris, in the Empire of France,
Chemist, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN PURIFYING ROCK AND SEA SALT," to be as follows:-
According to my first mode of proceeding, I take impure salts and melt
them in the open air in any suitable vessel, and when liquid I let them rest a
certain time, during which the earthy parts are precipitated. The chloride
of magnesium combined with the salt decomposes, and forms with the water
hydrochloric acid and magnesia. The first of these evaporates, the second is
precipitated to the bottom. By cooling the mass more or less quickly larger
or smaller crystals are obtained; these crystals are then pounded and sifted.
To facilitate this division the crystals or melted mass may be thrown hot into
water saturated with salt.
To operate by means of volatilization, I take these samo impure salts and

page_text: heat them red hot on the bottom of a furnace, or on an iron plate heated to
redness, on the surface of which a current of air is directed, which carries the
vapour arising from the chloride. of sodium into a condenser, where they
are condensed, and a salt as pure as snow thus obtained.
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 10th June 1857.
-
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Louis
JOSEPH FREDERIC MARGUERITTE, of Paris, in the Empire of France, Chemist,
end greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eleventh day of December, in the year of our Lord
One thousand eight hundred and fifty-six, in the twentieth 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 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 "IMPROVEMENTS IN PURIFYING ROCK AND SEA SALT,"
upon the condition (amongst others) that I, the said Louis Joseph Frédéric
Margueritte, 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 Louis Joseph Frédéric Margueritte, do
bereby 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, that is to say :-
The means heretofore employed in purifying soluble salts has consisted in
dissolving the substance and subsequently crystallizing it one or more times.
This operation, which has the advantage of being applicable to most kinds

page_text: of salts, is of long duration, expensive, and is effective only when often
repeated.
The process, which is the object of the present Patent to protect, is based on
fusion and crystallization by dry means, and also on the volatilization of the
material to be purified. A somewhat large number of combinations can bear
a great or a moderate heat without being decomposed, and could be sub-
mitted to this troatment; sea salt and rock salt are among the number.
It is known that sea salt is far from pure, and that it remains more or less
impregnated with its mother waters, which contain various salts, among others
a deliquescent substance, which is chlorido of magnesium; it is also known
that it is mixed with an earthy product, to which it owes its grey colour, and
which causes when dissolved its turbid appearance. Salt is for the most
part delivered for consumption and is used for culinary purposes in this
state. When it is desirable to refine it, it is necessary to dissolve it
again and cause it to evaporate in a pan or boiler. The means which I
propose for purifying it consists simply in fusing the raw salt, and keeping
it for some time in a state of tranquil fusion, decanting it into hot moulds,
or letting it cool slowly. In this manner all the impurities are separated
from the mass in fusion, and are eliminated by crystallization by the dry
process, which corresponds with crystallization by the wet process; two
layers are produced, of which the lower one is formed of foreign matters.
When the. cooling takes very long the salt crystallizes in form and aspect
quite analogous to the form and aspect assumed by rock salt; like the latter,
it is transparent, and presents an equal purity, and posseses the same physical
properties. When the cooling is rapid or sudden, the crystals are confused or
indistinct, less transparent, and less voluminous. In either case the mass,
previously crushed or pounded by submitting it to the action of a mill, is then
separated in various sizes. by means of sieves having meshes of various sizes.
This operation could bo advantageously applied to purifying rock salt. This
salt, which is perceptibly purer than sea salt, nevertheless contains earth and
foreign matters, which give it a brown, green, and sometimes a red colour,
and unfit it for immediate consumption. If the raw rock salt be fused on the
hearth of a furnace, for example, and maintained in a state of tranquil fusion
for some time, all the impurities settle at the bottom, the colouring disappears
by the oxidizing action of air, under the influence of heat, and if care be taken
to keep the current of air moist by a discharge of steam, the whole of the
chloride of magnesium is decomposed, & the- mass can then be poured off to
cool, or allowed to cool slowly. A mass of crystals, more or less transparent
according to the rapidity of the cooling, is so obtained, but they are white and

page_text: pure; sometimes crystals of considerable volume and perfect transparency are
produced, which are in every particular similar to rock salt. The inconvenience
arising from the density of this salt, and consequently the length of time
required for dissolving it, is counteracted by the greater subdivision of the
particles, and also by a particular state into which it enters when cooled in a
certain manner, so when the mass in fusion is allowed to run or flow into
cold water saturated with salt the crystals are suddenly decrepitated, and
become more friable and moro soluble on account of the infinite separation
of the particles.
The mechanical subdivision of rock salt thus purified will suffice in a great
number of cases, especially in the preparation of fine salt for the table, for
which application no other kind of salt could be compared with it as regards
purity, except that resulting from the precipitation of a salt liquid by
means of hydrochloric acid, or by washing with this acid, or with a saturated
solution of salt, which removes the chloride of magnesium and the other
salts.
The purification can be quickened by fusion, and by adding a small quantity
of carbonate of soda, which decomposes the magnesian and calcareous salts
which salt always contains. The quantity of carbonate of soda which may be
added varies according to the degree of impurity of the salt, but it should
never exceed one per cent. With one half per cent. good results are obtained;
with one quarter per cent. a fine produce is also obtained, but a longer time
is required than when one half or one per cent. is employed.
The advantages of this method of purifying over the processes heretofore
used are great as regards rapidity and economy, and are of much importance
to the consumer as regards the purity and quantity of the produco he buys,
inasmuch as common salt delivered for consumption contains the earthy
matters, salts of lime and of magnesia, which are far from wholesome, and
have the disadvantage of being hygrometric, and have the property of retaining
considerable quantities of water in the salt, the consumer is consequently
wronged in the quality and quantity of the salt; whereas salt purified in the
manner herein-before described is purged of all impurities, and among them of
chloride of magnesium, which becomes decomposed at the temperature
to which the salt is raised into hydrochloric acid, which becomes volatilized,
and into magnesia, which is separated in company with the other foreign
matters.
Lastly, I propose to purify sea and rock salt of all their impurities by
making them red hot on the hearth of a furnace, to the surface of which a
current of hot air is directed, which carries away the vapours of chloride of

page_text: sodium into a condenser, where they are held. By this means a salt is
obtained of great purity, perfectly separated, and of dazzling whiteness,
resembling snow.
Having described the nature of my Invention, and the manner of carrying
the same into effect, I declare that what I claim as my Invention, intended to
be protected by the herein-before in part recited Letters Patent, is,
First, the purification of sea and rock salt by tranquil fusion, and by
decanting or pouring off, or by, slow cooling, in the manner herein-before
described.
Secondly, the purification of sea and rock salt by tranquil fusion and by
adding carbonate of soda, as above described.
Thirdly, the purification of sea and rock salt by volatilization.
In witness whereof, I, the said Louis Joseph Frédéric Margueritte,
have hereunto set my hand and seal, this Third day of June, One
thousand eight hundred and fifty-seven.
LOUIS JOSEPH FREDERIC MARGUERITTE. (L.S.)