Iж• PROVEMENTS IN MANUFACTURING ALIZARIN AND ISOPURPURIN OUT OF AN- THRACEN
Year: 1874

page_text: LETTERS PATENT to Gustav Auerbach and Theodor Gessert, of
Elberfeld, in the Empire of Germany, for the Invention of "Iж•
PROVEMENTS IN MANUFACTURING ALIZARIN AND ISOPURPURIN OUT OF AN-
THRACEN."
"
Sealed the 25th September 1874, and dated the 13th April 1874.
PROVISIONAL SPECIFICATION left by the said Gustav Auerbach and
Theodor Gessert at the Office of the Commissioners of Patents, with
their Petition, on the 13th April 1874.
We, GUSTAV AUERBACH and THEODOR GESSERT, of Elberfeld, in the
Empire of Germany, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN MANUFACTURING ALIZARIN AND ISOPURPURIN OUT OF
ANTHRACEN," to be as follows:-
This Invention relates to a process for preparing alizarin and isopur-:
purin from anthracen. For this purpose wo heat anthracen with con-
centrated or fuming sulphuric acid to a high temperature. We dilute
the product with water, and neutralize it by the addition of an alkaline.

page_text: carbonate, such as carbonate of soda, or of lime, or baryta, or with
caustic alkali, such as soda or potash. The mixture then contains
the neutral sulphates of the alkaline bases employed, and acid
sulphates thereof. The neutral sulphates are then removed by filtration
or crystallisation, and the acid sulphates are neutralized by a farther
addition of carbonate of soda or of potash.
When carbonate of soda or of potash is used for neutralization in the
first instance it is not necessary to remove the sulphates of those alkalies,
from the neutralized product.
The product neutralized as above described, either in its dilute con-
dition or concentrated by evaporation, is then heated along with caustic
soda or potash to a temperature from 150° to 250° as long as a bluish or
red colour is produced. From this product we obtain a precipitate of
alizarin and isopurpurin on the addition of an acid.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Gustav Auerbach and Theodor Gessert in the Great
Seal Patent Office on the 30th September 1874.
:
TO ALL TO WHOM THESE PRESENTS SHALL COME, wc, GUSTAV'
AUERBACH and THEODOR GESSERT, of Elberfeld, in the Empire of
Gormany, send greeting:
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of April, in the year of
our Lord One thousand eight hundred and seventy-four; in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said Gustav Auerbach and Theodor Gessert,
Her special license that we, the said Gustav Auerbach and Theodor
Gessert, our executors, administrators, and assigns, or such other's as
we, the said Gustav Auerbach and Theodor Gessert, our exccutors,
administrators, and assigns, should at any time agree with, and no
others, from time to tinic and at all times thereafter during the term. 3
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the

page_text: .
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
MANUFACTURING ALIZARIN AND ISOPURPURIN OUT OF ANTHRACEN," upon the:
condition (amongst others) that we, the said. Gustav Auerbach and
Theodor Gessert, our executors or administrators, by an instrument in
writing under. our or their hands and seals, or under the hand and scal
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
DALL

page_text: anthracen.
In witness whereof, we, the said Gustav Auerbach and Theodor
Gessert, have hereunto set .our hands and seals, this Sixteenth
day of September, in the year of our Lord One thousand eight 5
hundred and seventy-four.