IMPROVEMENTS IN THE MANUFACTURE OP BENZOIC ACID
Year: 1865

page_text: LETTERS PATENT to François Alexandre Laurent and John Castbelaz,
both of Rue St. Croix de la Bretonnerie, Paris, in the Empire of France,
Manufacturers, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE
OP BENZOIC ACID."
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Sealed the 6th July 1865, and dated the 30th January 1865.
PROVISIONAL SPECIFICATION left by the said François Alexandro
Laurent and John Casthelaz at the Office of the Commissioners of
Patents, with their Petition, on the 30th January 1865.
We, FRANÇOIS ALEXANDRE LAURENT and JOHN CASTHELAZ, both of Rue
St. Croix de la Bretonnerie, Paris, in the Empire of France, Manufacturers,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF BENZOIC ACID," to be as follows:-
This Invention consists in transforming phthalic (naphthalic) acid into
benzoic acid.
The means we prefer to adopt for accomplishing this are as follows:-The
phthalic acid, in the state of a neutral salt of lime, and with an equivalent of
this same base added to it, is heated to a temperature of 380° to 350° Centi-
grade (626° to 662° Fahrenheit) for some hours. The necessary time varies
according to the temperature, and to the quantity of material that is being
acted on. During this operation it is necessary to avoid the presence of too
great a quantity of air. A current of air passing over these organic salts

page_text: when heated might produce a deflagration, and destroy a portion of the
material. When the materials have been sufficiently heated, the phthalate of
lime will have become changed into benzoate and carbonate of lime. The
benzoic acid is extracted by any well-known means; for example, by extracting
by water and precipitating by an acid.
We would state that the process above detailed is only given as an example
of the mode by which phthalic acid may be changed into benzoic acid, and
that the process may be greatly varied, either by varying the amount of lime,
or the degree of heat employed, or by employing, in place of lime, any other
base filling the same end.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said François Alexandre Laurent and John Casthelaz in the
Great Seal Patent Office on the 17th July 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, FRANÇOIS
ALEXANDRE LAURENT and JOHN CASTHELAZ, both of Rue St. Croix de la
Bretonnerie, Paris, in the Empire of France, Manufacturers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of January, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-eighth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
us, the said François Alexandre Laurent and John Casthelaz, Her special
licence that we, the said François Alexandre Laurent and John Casthelaz,
our executors, administrators, and assigns, or such others as we, the said
François Alexandre Laurent and John Casthelaz, our executors, adminis-
trators, 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 THE MANUFACTURE OF BENZOIC ACID,"
upon the
condition (amongst others) that we, the said François Alexandre Laurent and
John Casthelaz, our executors or administrators, by an instrument in writing
under our or their hands and seals, or under the hand and seal of one of us
or them, 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.

page_text: NOW KNOW YE, that we, the said François Alexandre Laurent and
John Casthelaz, 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 :-
This Invention has for its object the transforming phtalic acid into benzoic
acid.
For this purpose we decompose a salt of phtalic acid by means of heat
acting in conjunction with a suitable base. We prefer to proceed as follows:
-We produce phtalic acid by processes which are well known, either by the
oxidation of napthaline by means of bichromate of potash, permanganate of
potash, or oxide of lead, or it may be by the oxidation of bichloride of
naphtaline with nitric acid. We combine the phtalic acid with lime, so as to
produce a neutral phtalate of lime, and mix one equivalent of this salt with
one equivalent of bydrate of lime, and heat the mixture to a temperature of
from 330° to 350° Centigrade (say 626° to 662° Fahrenheit); this heat is
maintained for some hours. The time necessary for the process will vary to
some extent according to the heat employed and the quantity of material
operated on. A convenient quantity to treat at one operation is a mixture of
20 lbs. of neutral phtalate of lime and 4 lbs. of bydrate of lime. This mixture
we find it convenient to place in a cylinder of sheet iron, which is closed with
the exception of a small vent for the escape of the vapour of water which
may be produced in consequence of the materials being imperfectly dried. A
number of such cylinders are placed in tubes running through a pot or boiler
filled with melted lead. The heat is regulated to between 330° and 350°
Centigrade by means of a pyrometer. With the charge above named in each
cylinder, and at this temperature, the heat should be maintained for about 10
hours. The mixture when in a heated state should be protected from currents
of air, otherwise deflagration may take place, and a loss of material will
result. After being heated for a sufficient time the material will be found to
consist of a mixture of benzoate of lime and carbonate of lime. There are
many ways in which these substances may be separated, and the benzoic acid
obtained. The following, however, is the process we prefer :-The mixture,
when cold, is extracted by means of water with free steam blown into it, and
in this way it is boiled for several hours. The clear liquid is filtered off, and
the residue is extracted by two or three similar boilings. The benzoate of
lime is dissolved in the water whilst the carbonate remains undissolved. The
solution of benzoate of lime is concentrated, and treated with bydrochloric
acid, which precipitates the benzoic acid. When the liquid is cold it is

page_text: filtered, and the benzoic acid collected, washed with a small quantity of water,
and dried.
We would remark that in place of combining the phtalic acid with lime,
and then mixing the salt with a further quantity of lime, as above described,
other bases may be substituted; for example, baryta may be employed, but it
is more expensive.
What we claim is, the manufacturing benzoic acid by decomposing a salt
of phtalic acid by means of heat acting in conjunction with a suitable base, as
above described.
In witness whereof, we, the said François Alexandre Laurent and John
Castbelaz, have hereunto set our hands and seals, this Twentieth day
of June, in the year of Lord One thousand eight hundred and sixty-
F. A. LAURENT. (LS.)
(L.B.)
J. CASTHELAZ.
F. A. LAURENT. (LS.)
J. CASTHELAZ.
(L.B.)