IMPROVEMENTS IN THE EXTRACTION OF INDIGO AND OTHER SIMILAR SUB- SUBSTANCES FROM PLANTS > CONTAINING SUCH SUBSTANCES
Year: 1872

page_text: LETTERS PATENT to Christopher Webb Smith, of Highfield, near
Stroud, Gloucestershire, Manufacturing Chemist, for the Invention
of "IMPROVEMENTS IN THE EXTRACTION OF INDIGO AND OTHER SIMILAR SUB-
5
COMPLETE SPECIFICATION filed by the said Christopher Webb-Smith
at the Office of the Commissioners of Patents, with his Petition
and Declaration, on the 15th June 1872, pursuant to the 9th
Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHRISTOPHER
WEBB SMITH, of Highfield, near Stroud, Gloucestershire, Manufacturing
Chemist, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS
IN THE EXTRACTION OF INDIGO AND OTHER SIMILAR SUBSTANCES FROM PLANTS
> CONTAINING SUCH SUBSTANCES," and have petitioned Her Majesty to grant
unto my executors, administrators, and assigns, Her Royal Letters
Patent for the same, and have made solemn Declaration that I am
the first and true Inventor thereof.

page_text: NOW KNOW YE, that I, the said Christopher Webb Smith, do hereby
declare that the following Complete Specification, under my hand and
seal, fully describes and ascertains the nature of the said Invention,
and in what manner the same is to be performed, in and by the
following statement, that is to say:-
Various methods have been adopted for extracting indigo from the
ordinary indigo plants, but such methods have usually involved the use
of processes of maceration and fermentation which are uncertain and not
sufficiently under control to determine uniformity in their results, and
would not be found practically successful when applied to the wild
indigo plant. In treating plants containing indigo or other similar dye
substances I adopt the following improved process :—
I first separate the leaf coloring substance (chlorophyll) and other
substances not containing indigo by boiling or infusing the leaves
or other parts of the plant in a solution of carbonated alkali of the
strength of about from 1° to 1° "Beaume." Instead of the above men-
tioned alkali other solvents that will act in an analagous manner may be
used. The solution so obtained will not be found to contain indigo and
is therefore run off; the residium left is then subjected to a boiling
solution of from 2° to 5° Beaume of soda, caustic soda, potash, or lime, or
other analagous chemical agents.
I find it preferable to employ a mixture of lime of the proportion
of 10% of the weight of the dry leaf, and when the mixture is at the
boiling point I add a suitable quantity, varying from 1 to 3 per cent. of
the weight of the dry plant operated on, of stannous chloride and pro-
toscide of zinc, or either of them, or any other substance that is greedy
of or has a powerful affinity for oxygen. The boiling is continued
till the whole of the indigo is extracted and dissolved, which may be
ascertained by an examination of the treated plant. The solution so
obtained is then drawn off into suitable vessels and thrown down and
collected in the usual manner and dried off for sale or use.
The process
above described I employ with very beneficial results for treating and
extracting indigo from plants in the dried state. I also find that it
may be successfully applied to the spent plants or the residium thereof
after they have been submitted to the usual process for extracting the
indigo contained in them, but which after such process will be found
to contain a per-centage of blue owing to the imperfect operation of
the ordinary process. Such residium per-centage has hitherto been

page_text: ordinarily wasted, but by means of my improved process it may be
turned to account.
It will be found that by the employment of my improved process not
only will the operation of extracting the indigo be performed more
economically and efficiently and in a shorter time than by the old process,
but the product obtained will be of an uniformly superior quality.
In the use of indigo it has been an ordinary practice hitherto to
employ woad in the ordinary dye vat when woollen or other fabrics are
dyed. As a substitute for such use of woad from which comparatively
little coloring matter is extracted, I use the indigo plant as imported in a
dried state, and I prepare it for use by subjecting it to heat and grinding
it into a powder. In that state, or mixed up to form a paste, I employ
the pulverised indigo plant as a substitute for the woad, and find that it
gives greatly improved results and yields a large per-centage of coloring
matter.
Having now described my Invention, I would have it understood that
the details above described may, as will be well understood, be somewhat
varied; but what I claim as my Invention is, the employment of the
improved process of treating indigo and analagous plants and extracting
indigo and analagous substances substantially in the manner and for the
purpose above described. I also claim the preparation and use of the
dried indigo plant as a substitute for woad, in the manner and for the
purpose above described.
In witness whereof, I, the said Christopher Webb Smith, have
hereunto set my hand and seal, this Tenth day of June One
thousand eight hundred and seventy-two.
CHRISTOPHER WEBB SMITH. (L.S.)
Signed, sealed, and delivered by the
before-named Christopher Webb
Smith, in the presence of
WILBERFORCE HEELAS,
Solicitor,
Stroud.