Improvements relating to the Production of Pyro-catechine.
Year: 1893

page_text: Date of Application, 15th Nov., 1893
Complete Specification Left, 12th June, 1894-Accepted, 14th July, 1894
PROVISIONAL SPECIFICATION.
Improvements relating to the Production of Pyro-catechine.
I, JOHANN HEINRICH BAUM, of 28 Forsthausstrasse Frankfort-on-the-Main,
Sachsenhausen, in the Empire of Germany, Chemist, do hereby declare the nature
of this invention to be as follows:-
My invention relates to the production of pyrocatechine.
As L. Barth and M. v. Schmidt (Berl. Ber. XII 1260) have shown, a phenol-
disulpho-acid, which is obtained when sulphurizing phenol with fuming sulphuric
acid in a water bath, is transformed in a dioxybenzolmonosulpho-acid on fusion
with caustic potash or caustic soda, which acid by reason of its splendid green
ferric chloride reaction is probably characterized as a pyrocatechinemonosulpho-
acid. They concluded from the pyrocatechine and protocatechuic acid formed in
very small quantity on fusion with very much alkali (five times the quantity of
sulpho-acid) that they had in fact to deal with an ortho-dioxybenzolparasulpho-
acid. But they have not produced pyrocatechine from the pyrocatechinemono-
sulpho-acid almost exclusively formed. I have succeeded in transforming the
a phenoldisulpho-acid much more readily into this monosulpho-acid and converting
the latter into pyrocatechine itself, so that an agitation of the monosulpho-acid
with ether becomes quite superfluous. The pyrocatechinemonosulpho-acid formed
is then simply heated under pressure to between 180 and 220 degrees centigrade
with a 25 to 30 per cent. sulphuric acid and the pyrocatechine obtained is
withdrawn from the solution with ether. In lieu of sulphuric acid use may also be
made of other acids, such as for instance hydrochloric or phosphoric acid.
I will
hereinafter describe by way of example how my improved method is carried into
practice.
For producing pyrocatechinemonosulpho-acid I fuse 10 kilogrammes of sodium
a phenoldisulphonate with only 10 to 15 kilogrammes of caustic soda (Barth using
50 kilogrammes) for 8 to 10 hours in an autoclave at a pressure of between about
2 and 3 atmospheres at a temperature of 280 to 300 degrees centigrade.
A perfectly white mass is obtained which dissolves in dilute sulphuric acid with
energetic development of sulphurous acid and yields a colourless acid solution.
The acid solution is now neutralized with chalk, evaporated to a sirupy consistency
and allowed to cool. The sodium sulphate is precipitated and removed by filtering
or centrifugal action. The mother liquor forming a violet solution, which with
ferric chloride effects a beautiful green coloration, contains the pyrocatechine-
sulpho-acid formed, and this solution may serve directly for the production of
pyrocatechine.
For producing pyrocatechine from the monosulpho-acid I heat pyrocatechine-
monosulpho-acid, as which the before obtained solution may be employed, in an
appropriate autoclave with 10 kilogrammes of a 50 per cent. sulphuric acid to
between 180 and 220 degrees centigrade, giving a pressure of 15 to 20 atmospheres.
The dark solution obtained is now treated with steam until the distillate with ferric
chloride produces not a phenol reaction but a pyrocatechine reaction, is then
decoloured with a little animal charcoal, and the pyrocatechine agitated with ether.
In this manner more than 50 per cent. of the theoretical quantity of pyrocatechine
may be obtained.
Dated this 15th day of November 1893.

page_text: COMPLETE SPECIFICATION.
Improvements relating to the Production of Pyro-catechine.
I, JOHANN HEINRICH BAUM, of 28 Forsthausstrasse Frankfort-on-the-Main,
Sachsenhausen in the Empire of Germany, Chemist, do hereby declare the nature
of this 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 relates to the production of pyro-catechine.
As L. Barth and M. v. Schmidt (Berl. Ber. XII 1260) have shown, a phenol-
disulpho-acid, which is obtained when sulphurizing phenol with fuming sulphuric
acid in a water bath, is transformed into a dioxy-benzolmonosulpho-acid on fusion
with caustic potash or caustic soda, which acid by reason of its splendid green
ferric chloride reaction is probably characterized as a pyro-catechinemonosulpho-
acid. They concluded from the pyrocatechine and protocatechuic acid formed in
very small quantity on fusion with very much alkali (five times the quantity of
sulpho-acid) that they had in fact to deal with an ortho-dioxybenzol parasulpho-
acid. But they have not produced pyrocatechine from the pyrocatechinemono-
sulpho-acid almost exclusively formed. I have succeeded in transforming the
phenoldisulpho-acid much more readily into this mono-sulpho-acid and converting
the latter into pyrocatechine itself, so that an agitation of the monosulpho-acid
with ether becomes quite superfluous. The pyrocatechinemonosulpho-acid formed
is then simply heated with sulphuric acid of 25 to 30 per cent. under pressure to a
high temperature (preferably a temperature of from 180 to 220°) and the pyro-
catechine obtained is withdrawn from the solution with ether. In lieu of sulphuric
acid use may also be made of other acids, such as for instance hydrochloric acid or
phosphoric acid. I will hereinafter describe, by way of example, how my improved
method is carried into practice.
α
a
For producing pyrocatechinemonosulpho-acid I fuse 10 kilogrammes of sodium
phenoldisulphonate with only 10 to 15 kilogrammes of caustic soda (Barth using
50 kilogrammes) for 8 to 10 hours in an autoclave at a pressure of between about
2 and 3 atmospheres at a temperature of 280 to 300 degrees centigrade.
A perfectly white mass is obtained which dissolves in dilute sulphuric acid with
energetic development of sulphurous acid and yields a colourless acid solution.
The acid solution is now neutralized with chalk, evaporated to a sirupy consistency
and allowed to cool. The sodium sulphate is precipitated and removed by filtering
or centrifugal action. The mother liquor forming a violet solution which with
ferric chloride effects a beautiful green coloration, contains the pyrocatechine-
sulpho-acid formed and this solution may serve directly for the production of
pyrocatechine.
Production of pyrocatechine from the monosulpho-acid.
For this purpose pyrocatechinemonosulpho-acid, as which the before obtained
solution may be employed, is heated in a suitable autoclave with 10 kilogrammes of
a 50 per cent. sulphuric acid to a high temperature (a temperature of from 180 to
220 degrees centigrade, has been found suitable). The dark solution obtained is
now treated with steam until the distillate with ferric chloride produces not a
phenol reaction but a pyrocatechine reaction, it is then decoloured with a little
animal charcoal and the pyrocatechine agitated with ether. In this manner more
than 50 per cent. of the theoretical quantity of pyrocatechine may be obtained.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
First. The production of pyrocatechinemonosulpho-acid by melting a phenol-
disulpho-acid with only the same to one and a half the quantity of caustic alkali
under pressure and at an increased temperature.

page_text: Second. The transformation of pyrocatechinemonosulpho acid into pyrocatechine-
by heating the same with mineral acids, such as sulphuric acid, hydrochloric acid.
or phosphoric acid in an aqueous solution under pressure to a high temperature.
Dated this 12th day of June 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.