IMPROVE- MENTS IN THE MANUFACTURE OF NITRIC ACID AND CAUSTIC SODA, WHICH ARE ALSO APPLICABLE TO THE OBTAINING OF OTHER CHEMICAL PRODUCTS
Year: 1861

page_text: PROVISIONAL SPECIFICATION left by James Drysdale Malcolm at the
Office of the Commissioners of Patents, with his Petition, on the
16th April 1861.
I, JAMES DRYSDALE MALCOLM, of Brixton, in the County of Surrey,
Chemist, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE MANUFACTURE OF NITRIC ACID AND CAUSTIC SODA, WHICH ARE ALSO
APPLICABLE TO THE OBTAINING OF OTHER CHEMICAL PRODUCTS," to be as follows:-
My Invention consists in adding to the nitrate of soda, from which salt
nitric acid is generally manufactured, a substance with which the soda will not
combine, or with which it will not combine easily, at the temperature requisite
for effecting the separation or revolution therefrom of the nitric acid with
which it is in combination while in the form of nitrate of soda. There are
many such materials which might be used, but to illustrate in this my
Provisional Specification my method of procedure, I describe one method of
accomplishing the object:-I mix together intimately one part by weight of
nitrate of soda with three parts of fine clean sea sand, and introduce them
into a retort heated to redness (as in the ordinary manner of producing nitric
acid by the mutual action of nitrate of soda and sulphuric acid); the nitrous
fumes pass over and are collected or absorbed by water in the Woulfe's bottles
in the usual way, and the soda is left behind in the retort along with the sand
in the form of caustic soda, with perhaps a small portion of silicate of soda.
This residue when removed from the retort is immersed in a vessel of water,
when the caustic soda will be dissolved out from the mass, and the sand
remain at the bottom of the vessel, from which it can be collected and used
over and over again. If a proper degree of heat be not observed, the nitric

page_text: acid may become decomposed into its constituents oxygen and nitrogen, a
circumstance to be avoided in the production or evolution of nitric acid, but
which may be valuable in reference to cases where such decomposition is
required.
I have thus simply described a process so that the principle or feature of
my Invention may be understood, but I do not confine myself to the use of
sand only, as there are many other substances which I employ which are
similarly efficacious, and which I shall more particularly mention in my Final
Specification; neither do I confine myself to the relative proportions of the
materials mentioned, as others may on further experiment prove to be more
advantageous or convenient. From what has been said with regard to the
decomposition of the nitric acid by an unsuitable temperature for the evolution
of nitrous fumes, it will be evident that this my Invention can be used for the
production simply of caustic soda, or for the production jointly of caustic soda
and of nitric acid, or for the production of a mixture of oxygen and nitrogen
and caustic soda, or of silicate of soda (where sand is used), or of other pro-
ducts according to the nature of the salt to be decomposed, or the material
used in effecting its decomposition by the method indicated. In most chemical
processes mutual decomposition, or the exercise of what is termed elective
affinity, is the principle ordinarily acted upon. Thus the most usual method
of making nitric acid at present is to introduce into the retort nitrate of soda
and sulphuric acid. The nitrate being decomposed, and the nitrous fumes
being driven off and absorbed by the water in the Woulfe's bottles, the soda
unites itself with the sulphuric acid to constitute sulphate of soda. But by
the application of the principle of this my Invention, the soda or other
compound, or the greater portion of it, does not combine with the sand, but
continues to remain in its condition of caustic soda. The nature of this action
is, I believe, usually designated by chemists as catalytic.
What I intend to claim as my Invention is, the manufacturing or evolution of
nitric acid and the production of caustic soda by the method herein-before
described, and so far as the same principle or mode of action is indicated, the
application of such process to the decomposition of other materials by admixture
with others with which they will not or will only sparingly combine, so as to
evolve or produce other chemical products of value or utility in the arts.