Manufacture of Alpha-naphthylamine in an Easily Diazotisable and Stable Form.
Year: 1897

page_text: Date of Application, 18th Jan., 1897
Complete Specification Left, 11th Oct., 1897-Accepted, 13th Nov., 1897
PROVISIONAL SPECIFICATION.
Manufacture of Alpha-naphthylamine in an Easily Diazotisable and
Stable 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 (which has been communicated to me from abroad by The Farbwerke,
vormals Meister Lucius and Brüning, of Hoechst a/Main, in the Empire of
Germany, Chemical Manufacturers), to be as follows:-
Amongst the materials suitable for the production of insoluble azo dye stuffs on
the fibre, alpha-naphthylamine has been hitherto the most important, being
employed on account of the great beauty, fastness and cheapness of the Bordeaux
colour produced on the fibre by the combination of beta-naphthol and alpha-
naphthylamine.
The introduction of this azo colour to dyers and printers met at first with
considerable difficulties, which are not yet quite overcome. Apart from the easy
decomposition of the diazo-compound, the very manufacture of this intermediate
product encounters great difficulties. To produce the diazo-compound of
a-naphthyl-amine, the latter is, for the formation of hydrochlorate, brought into
solution with the requisite quantity of hydrochloric acid; the hydrochlorate thus
obtained is precipitated in the form of a fine paste by the addition of an excess
of hydrochloric acid requisite for diazotation and ice for cooling. By the addition
of a nitrite solution, the hydrochlorate thus obtained, can only be transformed
quantitatively into the diazo-compound, if it be separated in form of very fine
crystals. The manufacture of hydrochlorate in this finely divided and easily
diazotisable state, creates considerable difliculties to the dyer and printer, as the
slightest mistake on the part of the workman, for instance, in the quantity of acid
to be added in forming the hydrochlorate or in the mixing up of the hydrochlorate
solution with acid and ice, will lead to a badly diazotisable hydrochlorate paste,
the diazo solution of which produces poor results on the fibre as well as being
unstable.
To provide against these drawbacks, the manufacturers of alpha-naphthylamine
supplied the dyers and printers with a hydrochlorate obtained, as already stated,
by precipitating the solution. But here it was found, that by keeping this paste
for some time it changed into rough crystals and consequently into a totally useless
form, an accident which may easily happen, if the naphthylamine hydrochlorate
should fall into the paste, which, moreover, becomes decomposed by the influence
of light and air and therefore turns bad.
To obviate these disadvantages of the paste, an attempt was made to grind the
hydrochlorate and to supply the dyers and printers with it in a solid state. This
attempt however, failed, as the hydrochlorate was found to coagulate and conse-
quently gave bad results when diazotised. As a consequence the dyers and printers
returned to the paste or free base, in spite of its inherent drawbacks.

page_text: My correspondents have discovered, that a-naphthylamine may be obtained in
a stable form and fit for diazotation, without the above mentioned inconveniences,
by transforming the base into the sulphate and reducing the latter to a fine
powder. The alpha-naphthylamine sulphate may easily be ground to
a fine
powder-like mass, without fear of coagulation on being kept for a length of time.
All the dyer and printer need do is to stir it in water to a paste, without any
special precautions to be observed on their part:
This paste is quantitatively diazotisable on addition of ice and nitrate and gives
the best results.
1
Alpha-naphthylamine in this stable and, for diazotation, suitable form is manu-
factured by transforming the base into its sulphate and reducing the latter, after
carefully drying into powder by means of an appropriate mill.
The pulverulent alpha-naphthylamine sulphate thus obtained is a white dry
nowder.
Dated this 18+1, d...
1007
ABEL & IMRAY
Agents for the Applicant.
COMPLETE SPECIFICATION.
Manufacture of Alpha-naphthylamine in an Easily Diazotisable and
Stable Form.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, Chancery
Lane, in the County of London, Chartered Patent Agent, do hereby declare the
nature of this invention (which has been communicated to me from abroad by The
Farbwerke vormals Meister Lucius and Brüning, of Hoechst a/Main, in the Empire
of Germany, Chemical Manufacturers) and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
Amongst the materials suitable for the production of insoluble azo dye stuffs on
the fibre, alpha-naphthylamine has been hitherto the most important, being
employed on account of the great beauty, fastness and cheapness of the Bordeaux
colour produced on the fibre by the combination of beta-naphthol and alpha-
naphthylamine.
The introduction of this azo colour to dyers and printers met at first with
considerable difficulties, which are not yet quite overcome.
Apart from the easy decomposition of the diazo compound, the very manufacture
of this intermediate product encounters great difficulties.
To produce the diazo-compound of a-naphthylamine, the latter is, for the for-
mation of hydro-chlorate, brought into solution with the requisite quantity of
hydrochloric acid; the hydrochlorate thus obtained is precipitated in the form of
a fine paste by the addition of an excess of hydrochloric acid requisite for diazo-
tation and ice for cooling. By the addition of a nitrite solution, the hydrochlorate
thus obtained can only be transformed quantitatively into the diazo compound, if
it be separated in form of very fine crystals. The manufacture of hydrochlorate
in this finely divided and easily diazotisable state, creates considerable difficulties
to the dyer and printer, as the slightest mistake on the part of the workman, for
instance, in the quantity of acid to be added in forming the hydrochlorate or in
the mixing up of the hydrochlorate solution with acid and ice, will lead to a badly
diazotisable hydrochlorate paste, the diazo solution of which produces poor results
on the fibre as well as being unstable.

page_text: To provide against these drawbacks, the manufacturers of alpha-naphthylamine
supplied the dyers and printers with a hydrochlorate obtained, as already stated,
by precipitating the solution. But here it was found, that by keeping this paste
for some time it changed into rough crystals and consequently into a totally useless
form, an accident which may easily happen if the naphthylamine hydrochlorate
should fall into the condition of paste, which, moreover, becomes decomposed by
the influence of light and air and therefore turns bad.
To obviate these disadvantages of the paste, an attempt was made to grind the
hydrochlorate and to supply the dyers and printers with it in a solid state. This
attempt however failed, as the hydrochlorate was found to coagulate and conse-
quently gave bad results when diazotised.
As a consequence the dyers and printers returned to the paste or free base, in
spite of its inherent drawbacks.
My correspondents have discovered that a-naphthylamine may be obtained in
a stable form and fit for diazotation, without the above mentioned inconveniences,
by transforming the base into the sulphate and reducing the latter to a fine
powder. The alpha-naphthylamine sulphate when dried may easily be ground
to a fine powder-like mass, without fear of coagulation on being kept for a length
of time.
All the dyer and printer need do is to stir it in water to a paste, without any
special precautions to be observed on their part.
This paste is quantitatively diazotisable on addition of ice and nitrate and
gives the best results.
Alpha-naphthylamine in this stable and, for diazotation, suitable form is
manufactured by transforming the base into its sulphate and reducing the latter,
after carefully drying, into powder by means of an appropriate mill.
The pulverulent alpha-naphthylamine sulphate thus obtained is a white dry
powder.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed I declare that what I
claim is:
1. The herein described manufacture of a-naphthylamine in a form stable and
easily diazotisable by transforming the same into its sulphate, carefully drying
and finely pulverising.
2. The use of a-naphthylamine sulphate powder for production of diazo-
naphthaline.
Dated this 11th day of October 1807
ABEL & IMRAY
Agents for the Applicant.