IMPROVEMENTS IN THE MANUFACTURE OF OXALIC ACID
Year: 1865

page_text: LETTERS PATENT to John Casthélaz and Nicolas Basset, Chemists, both
of Rue Ste. Croix de la Bretonnerie, Paris, Empire of France, for
"
COMPLETE SPECIFICATION filed by the said John Casthélaz at the Office
of the Commissioners of Patents, with his Petition and Declaration on
the 9th September 1865, pursuant to the 9th Section of the Patent Law
Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, BE IT KNOWN
that we, JOHN CASTHELAZ and NICOLAS BASSET, Chemists, both of Rue Ste.
Croix de la Bretonnerie, Paris, Empire of France, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF OXALIC
ACID," 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 improvements in the manufacture of oxalic
acid, and consists in a mode of employing nitric acid as an oxidizing agent,
and also of employing certain matters not now. commonly used in the manu-
facture of oxalic acid. Heretofore the nitric acid employed for the pre-
paration of oxalic acid has been in a state of considerable concentration. We
have found that this is not desirable, and that the production of oxalic acid is
attained pefectly and more surely by means of nitric acid in a dilute state,

page_text: We have found by experience that the most suitable degree of dilution is 25°
of Beaumé's scale, nevertheless the result can be obtained with a much more
dilute acid. The matters we employ are all the substances containing
bydrogen and carbon at present used in this manufacture, but particularly
animal refuse of all sorts, and of this we give the preference to the flesh and
blood of horses, which is obtained readily from slaughter houses.
We can also employ glycerine, peat, leather, hare skins, and in short all
refuse of an albumenal nature.
The following is the manner in which we prefer to proceed:- We
submit solid matters to the action of steam of a pressure of about 8
atmospheres for the purpose of swelling them and commencing the disin-
tegration. The duration of this operation varies according to the nature of
the substances employed from one hour to four or five hours or more. It is
not required for liquid matters or matters which are already disintegrated.
The matters are then put into dissolving pans, heated in a sand, bath to a
temperature which may be allowed to rise gradually to 105° to 110° Centi-
grade. They are there mixed with an equal weight of nitric acid (sp. gr. 25°
Beaumé) to which is added ten per cent. of sulphuric acid (sp. gr. 66°) when
the solution is not produced with sufficient facility.
In subsequent operations no more sulphuric acid is added, the mother
liquors, which are herein-after spoken of, contain a sufficient proportion.
When the matters are dissolved the action of heat is continued until the
density of the liquid is raised to 40° Beaumé, or thereabout, and until the
fatty matters isolated by the reaction have risen to the surface and been
removed with care. Nitric acid (sp. gr. 25°) is then added, little by little,
in the proportion of one-tenth of the volume of the liquid, which then takes a
beautiful amber tint. When the reaction is terminated the liquid is put aside
to crystallize. The mother liquors of the first crystallization are mixed with
their volume of nitric acid (sp. gr. 25°) is introduced into a large stoneware
vessel heated in a water bath, and to this vessel is adapted a series of Woolf's
receivers to condense the nitric vapours, and the product serves for future
operations. The water bath is heated until reddish vapours commence
appearing; the operation is finished when these vapours have ceased. The
liquid residue is then submitted to a second crystallization. The mother
liquors of the second crystallization, which are still rich in organic matter and
in nitric and sulphuric acids, serve for the solution of an equal weight of fresh
matter, which has already been prepared with steam; only a tenth of nitric
acid (sp. gr. 25) is added to complete the reaction after the fatty matters
have been removed; and the operation is the same for all 'the subsequent first

page_text: crystallizations. The mother liquors of the first crystallization are in each
case taken back to the apparatus for distilling off and collecting some of the
nitric acid it contains, and the mother liquors of the second crystallizations
serve indefinitely for the solution of fresh material. The purification of the
crystals obtained is effected by the ordinary processes. The process above
described may be varied to some extent according to the nature or facility of
solution of the matters employed by diminishing, increasing, or omitting the
action of steam, by diminishing, increasing, or omitting the sulphuric acid,
or further by increasing or diminishing the proportion of nitric acid, but
conforming still to the principles of the process above described.
In witness whereof, we, the said John Casthelaz and Nicolas Basset,
have hereunto set our hands and seals, this Seventh day of September,
in the year of our Lord One thousand eight hundred and sixty-five.
JOHN CASTHELAZ: (L.S.)
NICOLAS BASSET. (LS.)