IMPROVEMENTS IN PRESERVING POTATOES
Year: 1867

page_text: LETTERS PATENT to James Dewar, Doctor of Medicine, residing in
Kirkcaldy, in the County of Fife, in North Britain, for the Invention
of "IMPROVEMENTS IN PRESERVING POTATOES."
Sealed the 20th March 1868, and dated the 30th September 1867.
PROVISIONAL SPECIFICATION left by the said James Dewar at the Office
of the Commissioners of Patents, with his Petition, on the 30th September
1867.
I, JAMES DEWAR, Doctor of Medicine, residing in Kirkcaldy, in the County
of Fife, in North Britain, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PRESERVING POTATOES," to be as follows:-
My Invention consists in subjecting potatoes to the action of sulphurous
acid for the purpose of preserving them in a condition suitable for food.
I immerse the potatoes either whole or divided into slices or pieces in
sulphurous acid of the strength indicated in the British Pharmacopoeia or
diluted with water. Sulphurous acid of the strength above specified diluted
with an equal bulk of water forms an advantageous mixture for the purpose.
I find an immersion of one hour sufficient, after which I dry the potatoes and
keep them dry until required for use.

page_text: The potates whole or divided into slices or pieces may be coated with
a mixture of sulphurous acid and mucilage either by dipping them in the
mixture or by applying the mixture with a brush or otherwise to the surfaces.
The sulphurous acid may, be of the strength indicated in the British
Pharmacopoeia; the mucilage may be of gum or starch of a consistency
similar to that of the mucilage of gum acacia indicated in the British
Pharmacopoeia, and the acid and mucilage may conveniently be mixed in
equal parts by measure; the potatoes should then be dried as speedily as may
be, and kept dry until they are required for use.
I prefer to remove the skins of the potatoes before applying the acid, but
they may be preserved as above mentioned without removal of the skins.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said James Dewar in the Great Seal Patent Office on the 25th
March 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
DEWAR, Doctor of Medicine, residing in Kirkcaldy, in the County of Fife, in
North Britain, send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of September, in the year of our Lord
One thousand eight hundred and sixty-seven, in the thirty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said James Dewar, Her special licence, that I, the said James Dewar, my
executors, administrators, and assigns, or such others as I, the said James
Dewar, 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 PRESERVING
POTATOES," upon the condition (amongst others) that I, the said James Dewar,
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.

page_text: NOW KNOW YE, that I, the said James Dewar, 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:-
My Invention consists in subjecting potatoes to the action of sulphurous
acid for the purpose of preserving them in a condition suitable for food, as
herein-after mentioned. I do not saturate the substance of the potato
throughout with the acid, but merely subject. the surface to the action
thereof.
My Invention does not require the use of any sulphite or salt to preserve
the potatoes.
The manner in which my Invention is to be performed is as follows:-I
immerse the potatoes which I intend to preserve, either whole or in pieces,
in sulphurous acid diluted with water. The sulphurous acid which I employ
is the aqueous solution of ordinary commercial strength, say, of specific gravity
about 1012. The acid solution of that strength diluted with an equal bulk
of recently distilled water or water recently boiled and allowed to cool forms
an advantageous mixture for the purpose. I find an immersion in that
mixture of one hour's duration sufficient, after which I pour or run off the
mixture and close the vessel in which the potatoes are contained and keep it
closed, or if I do not intend to keep the potatoes in a closed vessel I dry them
thoroughly by exposure to dry air of a temperature from sixty to one hundred
and forty degrees of Fahrenheit, according as the drying is desired to be
done less or more rapidly, and subsequently keep them dry until required for
use.
Another manner of performing my Invention is to coat the potatoes whole
or in pieces with a mixture of the aqueous solution of sulphurous acid of tho
ordinary commercial strength before mentioned and mucilage, either by
dipping them in the mixture or by applying the mixture with a brush or
otherwise to the surfaces. The mucilage I employ for the purpose is gelatine,
gum, dextrine, or starch dissolved in a quantity of recently distilled water or
water recently boiled and allowed to cool, sufficient to produce a mucilage of
a consistency similar to that of gum acacia (otherwise gum arabic) indicated
in the British Pharmacopoeia. The mixture of the said solution and mucilage
which I find most suitable for the purpose is composed of equal parts by
measure of each. A complete coating of this mixture having been given to
the surfaces that coating should be thoroughly dried, which is best done by
exposure to dry air of a temperature of. from sixty to one bundred and forty
degrees of Fahrenheit, according as the drying is desired to be done less or

page_text: more rapidly. The potatoes thus treated should be kept dry until required
for use.
In preserving potatoes in any of the modes herein-before described I prefer
to remove the skins before subjecting them to the acid; but they may be
preserved, as above mentioned, without removal of the skins.
In witness whereof, I, the said James Dewar, have hereunto set my
hand and seal, this Twenty-first day of March, in the year of our Lord
One thousand eight hundred and sixty-eight.
JAMES DEWAR. (L.B.)