Improved Process for Intensifying Photographic Silver Prints.
Year: 1899

page_text: Date of Application, 1st Apr.,
1899
PROVISIONAL SPECIFICATION.
Improved Process for Intensifying Photographic Silver Prints.
I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton
Buildings, in the County of London, Consulting Engineer and Chartered Patent
Agent, do hereby declare the nature of this invention (as communicated to me
from abroad by Actien Gesellschaft für Anilin Fabrikation, of Berlin, in the
Empire of Germany, Chemical Manufacturers), to be as follows:-
For intensifying photographic silver prints (negatives or positives), especially
in the negative process with bromide of silver gelatine, two methods have
heretofore been principally used.
The first method consists in using mercuric chloride as intensifier, by the
action of which the black silver print is first bleached, assuming a greater
transparency. After washing thoroughly, the print is again densified and
darkened by treatment with ammonia or sodium sulphite, whereupon it is
washed once more.
This
The second method consists in using as intensifiers uranium salts.
process only requires one operation, however the intensive red-brown colour
produced in the print by the action of the uranium salts is not at all stable and
besides the degree of the intensification attained can not be safely calculated.
Moreover the uranium intensifier does not keep, but is decomposed in a short
time.
My correspondents have now found that the double-salts of mercuric thio-
cyanate yield solutions which keep well and which intensify the photographic
silver-print with black colour in one single operation.
Of the double-salts of mercuric thiocyanate, especially those formed with
thiocyanates of the alkalies, alkaline earths and ammonia can be practically
used.
The invention is illustrated by the following example:
10 parts of mercuric thiocyanate and
8
100
"
"
33
دو
potassium thiocyanate are dissolved in
distilled water.
'
This stock-solution which can be kept without decomposing is diluted with
10 parts of water for use as intensifier.
The negative or positive which needs intensifying, is placed into the diluted
solution and left therein, while preferably keeping the liquid in motion, until
the desired degree of intensification is reached. The intensified negative or
10 parts of mercuric thiocyanate and
8
100
99
"
33
دو
potassium thiocyanate are dissolved in
distilled water.
.
This stock-solution which can be kept without decomposing is diluted with
10 parts of water for use as intensifier.
The negative or positive which needs intensifying, is placed into the diluted
solution and left therein, while preferably keeping the liquid in motion, until
the desired degree of intensification is reached. The intensified negative or
positive is then washed and dried.
ABEL & IMRAY,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improved Process for Intensifying Photographic Silver Prints.
I, CHARLES DENTON ABEL, of Birkbeck Bank Chambers, Southampton
Buildings, in the County of London, Consulting Engineer and Chartered Patent
Agent, do hereby declare the nature of this invention (as communicated to me
from abroad by Actien Gesellschaft für Anilin Fabrikation, of Berlin, 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:-
For intensifying photographic silver prints (negatives or positives), especially
in the negative process with bromide of silver gelatine, two methods have
heretofore been principally used.
The first method consists in using mercuric chloride, as intensifier, by the
action of which the black silver print is first bleached, assuming a greater
transparency. After washing thoroughly, the print is again densified and
darkened by treatment with ammonia or sodium sulphite, whereupon it is
washed once more.
This
The second method consists in using as intensifiers uranium salts.
process only requires one operation, however the intensive red-brown colour
produced in the print by the action of the uranium salts is not at all stable and
besides the degree of the intensification attained can not be safely calculated.
Moreover the uranium intensifier does not keep, but is decomposed in a short
time.
My correspondents have now found that the double-salts of mercuric thio-
cyanate yield solutions which keep well and which intensify the photographic
silver-print with black colour in one single operation.
Of the double-salts of mercuric thiocyanate, especially those formed with
thiocyanates of the alkalies, alkaline earths and ammonia can be practically
used.
The invention is illustrated by the following example.
The invention is illustrated by the following example:

page_text: subjecting them to the action of a solution containing a double salt of mercuric
thiocyanate with a thiocyanate of an alkali, an alkaline earth, or ammonia,
together with an excess of the alkali thiocyanate.
Dated this 8th day of December 1899