The Preparation and Employment of Aromatic Amido Compounds as Developing Means in Photography.
Year: 1891

page_text: Date of Application, 11th Sept., 1891
Complete Specification Left, 26th May. 1892-Accepted, 3rd Sept., 1802
PROVISIONAL SPECIFICATION.
The Preparation and Employment of Aromatic Amido Compounds as
Developing Means in Photography.
I, JULIUS HAUFF, of Feuerbach, near Stuttgart, Germany, Manufacturer, do
hereby declare the nature of this invention to be as follows:-
A. and L. Lumière drew attention to the fact that paramido-phenol had very
strong reducing properties, and was therefore applicable to the development of
photographs. This developing means was experimented upon by Prof. Dr. Eder
of Vienna and highly recommended for use in the practice of photography.
I have now discovered that the amido-cresol and xylenol possessed these reducing
properties to a much higher extent, and that developing solution made therewith
had an almost unlimited durability being still less easily colored than the amido-
phenol solution.
In the course of further experiments triamido-phenol, amido-dioxy-benzol have
been found useful for the development of photographs as well as the amido-com-
pounds of aromatic oxycarbonic acid and a series of alkylized amido-compounds.
These substances are:

page_text: The peculiar circumstance is that the above acids develop photographs when
ombined with caustic alkalies while the amide acids produce the same result with
lkaline.carbonates. Example, 1 gr. of amido-cresotin-amide is dissolved in 100 gr.
f water with 4 gr. of sulphite of soda, and 3 gr. of potash. These acids are highly
uitable as developing means and give moreover clearer results than the rapidly
leveloping hydroquinones.

page_text: The di-alkylized products of phenylene diamine are characterized by their ready
solubility and great durability in the developing solutions formed therewith. As
already stated 1% solutions in combination with alkaline carbonates develop
rapidly and intensely.
The tetra-alkylized products are less soluble in water. Above all others how-.
ever are the di-alkylized amido phenols which are as yet unsurpassed by any other
compound for developing power and rapidity; the durability of their solutions is
still greater than that of the ordinary amido-phenols.
The features of the invention are the employment of amido compounds here-
under enumerated for the development of photographs in layers containing halogen
silver:

page_text: COMPLETE SPECIFICATION.
The Preparation and Employment of Aromatic Amido Compounds as
Developing Means in Photography.
JULIUS HAUFF of Feuerbach, near Stuttgart, Germany, Manufacturer 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 amido phenols such as p-amido phenol and the two p-amido-cresols which
have been so highly praised of late as developing means for photographic purposes
have the defect that they are so slightly soluble as to necessitate for their use a
recourse to caustic alkalies which are in many ways unsuitable in the practice of
photography.
The use of caustic alkalies is likewise needed for the development of the photo-
graphic image with p-phenylene-diamines the use of which is protected by German
Letters Patent, No. 46915 dated 1st August 1888 but has now been freely given up,
as great inconvenience resulted from the use of caustic alkalies.
I have remedied these defects by alkylizing the amnido group through which I
obtain in the p-amidophenol such a solubility as will allow the exclusive use of
carbonates of the alkalies, while in the phenylene-diamine I not only obtain à
greater solubility but increase the developing power in such a manner as to allow of
the use of carbonates of the alkalies.
For the development of photographic images the following compounds are
used