Improvements in the Manufacture of Primary Disazo Dyestuffs.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Primary Disazo Dyestuffs.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by Leopold Cassella and Company of Frankfort on Main in the Empire of
Germany) to be as follows:-
As is known phenol can be combined with two molecules of diazo bodies to form
primary disazo dyestuffs, whilst hithereto only monoazo dyestuffs have been
obtained from its ortho and para-substitutes.
My foreign correspondents have now found that salicylic acid is able to take up
two azo groups.
For performing the process the easily soluble monoazo dyestuffs which result
from diazosulpho acids and salicylic acid are the best. Energetically reacting
diazo derivatives, such as nitrodiazo-benzole may advantageously be used as the
second diazo compound.
Example. 416 parts by weight of the dyestuff from 2-7 diazo naphthalene-
sulpho acid and salicylic acid (which as known dyes wool yellow) are brought.
together in dilute solution with the diazo compound produced from 13.8 parts
by weight of p. nitraniline; the liquor is kept alkaline during the operation by
means of carbonate of soda. A precipitate of the primary disazo dyestuffs is
immediately formed which after a few hours is filtered aff. It dyes chromed wool
brown.
In an analogous manner brown chrome-dyestuffs result, if in the first place
another diazonaphtalenesulpho acid or also diazobenzole sulphoacid, diazoazo-
benzolesulpho acid etc., and in the second place for instance ortho or meta-
nitraniline or nitrotoluidine are employed. The resulting dyestuffs are especially
fast to light and dye very much more level than the monoazoderivatives of salicylic
acid, moreover the introduction of an azo group in the ortho position to the
hydroxyle, makes the least sensitiveness towards alkalis disappear.
Dated this 7th day of August 1896.
SYDNEY PITT.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Primary Disazo Dyestuff's.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by Leopold Cassella and Company, of Frankfort on Main, in the Empire.
of Germany,) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:—
As is known phenol can be combined with two molecules of diazo bodies to form
primary disazo dyestuffs, whilst hitherto only monoazo dyestuffs have been obtained
from its ortho and para-substitutes.

page_text: My foreign correspondents have now found that salicylic acid is able to take up
two azo groups.
For performing the process the easily soluble monoazo dyestuffs which result
from diazosulpho acids and salicylic acid are the best. Energetically reacting
diazo derivatives, such as nitrodiazo-benzole may advantageously be used as the
second diazo compound.
Example. 416 parts by weight of the dyestuff from 2-7 diazo naphtalene-
sulpho acid and salicylic acid (which as known dyes wool yellow) are brought
together in dilute solution with the diazo compound produced from 13-8 parts
by weight of p. nitraniline; the liquor is kept alkaline during the operation by
means of carbonate of soda. A precipitate of the primary disazo dyestuffs is
immediately formed which after a few hours is filtered off. It dyes chromed wool
brown.
In an analogous manner brown chrome-dyestuffs result, if in the first place
another diazonaphtalene-sulpho acid or also diazobenzole sulphoacid, diazoazo-
benzolesulpho acid etc., and in the second place for instance ortho or meta-
nitraniline or nitrotoluidine are employed. The resulting dyestuffs are especially
fast to light and dye very much more level than the monoazoderivatives of salicylic
acid, moreover the introduction of an azo group in the ortho position to the
hydroxyle, makes all sensitiveness towards alkalis disappear.
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 :-
1. Producing primary disazo dyestuffs by combining one molecule of salicylic
acid with two molecules of diazo bodies substantially as described.
2. The new primary disazo dyestuff to which this specification relates.
11
T
SYDNEY PITT.