Manufacture of Stable Diazo-compounds in Concentrated Liquid or Solid Form.
Year: 1894

page_text: Date of Application, 5th Nov., 1894
Complete Specification Left, 6th Aug., 1895-Accepted, 7th Sept., 1895
[Communicated from abroad by THE FARBWERKE, vormals MEISTER LUCIUS
& BRUNING, of Hoechst a/ Main, in the Empire of Germany, Chemical
Manufacturers.]
Manufacture of Stable Diazo-compounds in Concentrated Liquid
or Solid Form.
1. OLIVER IMRAY, of No. 28, Southampton Buildings, Chancery Lane, in the
County of London, Chartered Patent Agent, do hereby declare the nature of this
invention to be as follows:-
The method of obtaining azo-dyes by combining their components in the fibre,
which has been for some years practised, has become one of the most important
processes in printing and dyeing, but notwithstanding the beauty and fastness of
the dyes thus produced, its development and general application has been retarded
by one circumstance.
Since the diazo-compounds necessary to the production of the dyes in question
cannot be obtained ready made on account of their instability, the dyer or printer
is obliged to make the diazo-solutions himself every time that he requires them,
and this inconvenient expensive and, for the dyer, often difficult operation interferes
with full practical development of the process.
It has, therefore, long been a problem to bring the diazo compounds into a stable
transportable form in order to be able to supply the dyer and printer with the
ready made material.
My foreign correspondents have obtained this end in an entirely new way.
They have discovered the remarkable fact that the diazo-compounds become so
stable in presence of an excess of mineral acid i.e. more acid than is necessary for
diazotising, that they may be continuously subjected to a temperature of about
45° C. without decomposition and thus may be concentrated, or evaporated to
dryness. Thus diazo-compounds are obtained in concentrated liquid or in solid
form, which are very stable and dissolve easily in water, and these solutions may
be employed without further treatment for the production of the dye on the fibre
in the usual manner.
The danger due to the inflammability of the diazo-compounds is removed or
diminished by mixing them with incombustible substances such as sulphate of
alumina or sodium sulphate, or by adding these substances to the solution before
evaporating.
The concentrated diazo-solutions which are to be used in the form of paste or
syrup are not inflammable, but even in these cases the addition of such a diluent
is advisable in order that should the diazo-compound become dry, its inflammability
may not exceed the limits of safety.
The diazo solutions evaporated to a syrupy consistence may be brought into the
form of a dry powder by the admixture of a quantity of a substance which absorbs
water such as anhydrous sodium sulphate or calcined alum.

page_text: The diazo-compound of para nitraniline may be prepared with a small excess of
acid, about 5% more than the theory requires; such a solution freshly prepared
acts perfectly as a diazo-compound for making dyes. It is however not possible to
keep the solution as, after standing for some time at the ordinary temperature
partial decomposition sets in and a dirty yellow precipitate is formed. The
decomposition proceeds rapidly at higher temperatures.
The diazo solution behaves quite differently if it is mixed with a considerable
excess of acid (about 50% more than the theory requires) immediately after it has
been prepared or if this excess is added before diazotising.
A solution prepared in this way is not only stable at ordinary temperatures but
also at higher temperatures for a considerable time and thus its concentration is
possible.
14 kilos. para-nitraniline are diazotised with
7
sodium nitrite and
"
17
"
sulphuric acid 66° Bé.
in the usual way but in aqueous solution as concentrated as possible. The diazo-
solution is filtered and concentrated in a vacuum-apparatus of lead or copper at a
temperature not exceeding 45° C. When the concentrated mass has become
syrupy or a paste it is taken out of the apparatus and mixed with an equal quantity
by weight of anhydrous sodium sulphate or calcined alum, and thus it is obtained
in the form of a dry powder; or 50 kilos. of sodium sulphate, or 15 kilos. of alum,
are added to the diazo-solution which is then evaporated to dryness.
For the excess of sulphuric acid in the above example may be substituted hydro-
chloric acid or acid salts such as sodium bisulphate or sulphate of alumina. These
salts seem to be specially favourable for the stability of the diazo solution.
ABEL & IMRAY,
Agents for the Applicant.
Manufacture of Stable Diazo-compounds in Concentrated Liquid
or Solid Form.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Chartered Patent Agent, 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:-
The method of obtaining azo dyes by combining their components in the fibre,

page_text: which has been for some years practised, has become one of the most important
processes in printing and dyeing, but notwithstanding the beauty and fastness
of the dyes thus produced, its development and general application has been
retarded by one circumstance.
Since the diazo compounds necessary to the production of the dyes in question
cannot be obtained ready made on account of their instability, the dyer or printer
is obliged to make the diazo solutions himself every time that he requires them,
and this inconvenient expensive and, for the dyer, often difficult operation, interferes
with full practical development of the process.
It has, therefore, long been a problem to bring the diazo compounds into a stable
transportable form in order to be able to supply the dyer and printer with the
ready made material.
My foreign correspondents have obtained this end in an entirely new way.
They have discovered the remarkable fact that the diazo compounds become so
stable in presence of an excess of mineral acid i.e. more acid than is necessary for
diazotising, that they may be continuously subjected to a temperature of about 45° C.
without decomposition and thus may be concentrated, or evaporated to dryness.
Thus diazo compounds are obtained in concentrated liquid or in solid form, which
are very stable and dissolve easily in water, and these solutions may be employed
without further treatment for the production of the dye on the fibre in the usual
manner.
The danger due to the inflammability of the diazo compounds is removed or
diminished by mixing them with incombustible substances such as sulphate of
alumina or sodium sulphate, or by adding these substances to the solution before
evaporating.
The concentrated diazo solutions which are to be used in the form of paste or
syrup are not inflammable, but even in these cases the addition of such a diluent
is advisable in order that should the diazo compound become dry, its inflammability
may not exceed the limits of safety.
The diazo solutions evaporated to a syrupy consistence may be brought into the
form of a dry powder by the admixture of a quantity of a substance which absorbs
water such as anhydrous sodium sulphate or calcined alum.
The diazo compound of para-nitraniline may be prepared with a small excess of
acid, about 5% more than the theory requires; such a solution freshly prepared
acts perfectly as a diazo-compound for making dyes. It is however not possible to
keep the solution as after standing for some time at the ordinary temperature partial
decomposition sets in and a dirty yellow precipitate is formed."
The decomposition proceeds rapidly at higher temperatures.
The diazo solution behaves quite differently if it is mixed with a considerable
excess of acid (about 50% more than the theory requires) immediately after it has
been prepared or if this excess is added before diazotising.
A solution prepared in this way is not only stabie at ordinary temperatures but
also at higher temperatures for a considerable time and thus its concentration is
14 kilos. para-nitraniline are diazotised with
7
sodium nitrite and
"
17
sulphuric acid 66° Bé.
כל
0 in the usual way but in aqueous solution as concentrated as possible. The diazo
solution is filtered and concentrated in a vacuum-apparatus of lead or copper at a
temperature not exceeding 45° C. When the concentrated mass has become syrupy
or a paste it is taken out of the apparatus and mixed with an equal quantity by

page_text: weight of anhydrous sodium sulphate or calcined alum, and thus it is obtained in
the form of a dry powder; or 50 kilos. of sodium, sulphate, or 15 kilos. of alum,
are added to the diazo solution which is then evaporated to dryness.
For the excess of sulphuric acid in the above example may be substituted
hydrochloric acid or acid salts such as sodium bisulphate or sulphate of alumina.
'These salts seem to be specially favourable for the stability of the diazo solution.
For the excess of sulphuric acid in the above example may be substituted
hydrochloric acid or acid salts such as sodium bisulphate or sulphate of alumina.
"These salts seem to be specially favourable for the stability of the diazo solution.
2.
DIAZO-DIANISIDINE.
25 kilos. dianisidine are diazotised with
14
35
"
99
sodium nitrite and
sulphuric acid of 66° Be.
in the usual manner in aqueous solution as concentrated as possible, and the diazo
solution, after being filtered, is evaporated with the addition of 60 kilos. of alum
in a vacuum apparatus with the precaution that the temperature of 45° C. is not
exceeded. The process is otherwise the same as in the case of para-nitraniline.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The manufacture of stable soluble non-explosive diazo compounds in the
form of paste or powder by concentrating or evaporating to dryness diazo solutions
at low temperatures in presence of a quantity of mineral acid greater than is
absolutely necessary for the diazotation, or in presence of acid salts such as sulphate
of alumina, which can be substituted for the excess of acid, and by adding a body
which prevents the explosiveness of the diazo solution to the solution or to the
pasty or dry diazo compound.
2. The stable diazo compounds manufactured as above set forth.
1
T
ABEL & IMRAY,
Agents for the Applicant.