IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF COLLODIO-BROMIDE OF SILVER EMULSION, AND PREPARING PHOTOGRAPHIC DRY PLates therewITH."
Year: 1880

page_text: LETTERS PATENT to Julius. Hermann Guido Wolfram, of Dresden, in the
Kingdom of Saxony, Chemist, for an Invention of "IMPROVEMENTS IN THE
MANUFACTURE OR PRODUCTION OF COLLODIO-BROMIDE OF SILVER EMULSION,
AND PREPARING PHOTOGRAPHIC DRY PLates therewITH."
PROVISIONAL SPECIFICATION left by the said Julius Hermann Guido
Wolfram at the Office of the Commissioners of Patents on the 26th February
1880.
"
JULIUS HERMANN GUIDO WOLFRAM, of Dresden, in the Kingdom of Saxony,
Chemist. IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF COLLODIO-
BROMIDE OF SILVER EMULSION, AND PREPARING PHOTOGRAPHIC DRY PLATES
THEREWITH,”
This Invention consists in,-
1st. The preparation of a modification of collodio-bromide of silver emulsion of
high sensitiveness by producing the bromide of silver in the presence of a sufficient
quantity of liquor ammonia.
2nd. The preparation of dry plates for photographic purposes by means of
collodio-bromide of silver, the object being to render thein as sensitive (or
approximately so) as gelatino-bromide plates.
Collodio-bromide of silver emulsion prepared as heretofore usual produces
photographic dry plates of a very inferior sensitiveness.
Collodion prepared according to this Invention renders it possible to produce dry
plates for photographic purposes equal (or approximately so) in sensitiveness to
gelatino-bromide of silver plates.
The adding of liquor ammonia to ready made collodio-bromide of silver emulsion
and allowing it to react thereon for a considerable period so as to convert the
bromide of silver into its highest state of sensitiveness, does not produce a result
so satisfactory as that obtained by the use of the preparation of gelatino-bromide
of silver emulsion. Now I have found that in order to obtain a good result with
collodio-bromide of silver, it is essential such bromide of silver should be produced
in the presence of a sufficient quantity of liquor ammonia, and collodio-bromide of

page_text: silver emulsion according to my Invention may be prepared in the following
manner (that is to say):
I add to 100 grammes of collodion, which contains 2 per cent. of pyroxyline, a
solution consisting of 4 grammes of nitrate of silver dissolved in 15 grammes of
concentrated liquor ammonia and 15 grammes of absolute alcohol. I further add 5
sufficient alcohol of 40 or 50 per cent. to re-dissolve all the silver salts that have
been precipitated. I then add a solution consisting of bromide of potassium, or
bromide of sodium, or bromide of ammonium dissolved in 10 grammes of liquor
ammonia to which 10 grammes of alcohol are added. The quantity of the above
named bromide of potassium, or of sodium, or of ammonia may be equivalent to
the quantity of nitrate of silver used, but I prefer to use the bromide a little in
excess of the nitrate of silver.
This solution is added to the collodion shaking or agitating violently at the
same time. As soon as a uniform mixture is obtained the mixture of pyroxyline
and bromide of silver is precipitated by the addition of a large quantity of water; 1
the precipitato is then freed from ammonia and salt by decantation, afterwards
dried and dissolved in 100 to 200 grammes of other alcohol, to which 1 to 3 per
cent. of glycerine and any suitable kind of preservative may be added.
The quantity named for nitrate of silver and liquor ammonia may be varied
according to circumstances, 2 to 6 grammes of nitrate of silver or 2 to 30 grammes
of liquor ammonia may be used.
According as the quantity of liquor ammonia is increased the sensitiveness of
the emulsion will be heightened. Instead of nitrate of silver any other salt of
silver soluble in liquor ammonia may be employed.
It is to be understood that the preparation of collodio-bromide of silver emulsion,
as above, as well as the preparation of dry plates by means of such emulsion can
take place only in a room faintly illuminated by red light.

page_text: DIECIFICATION In pursuance of the conditions of the Letters fatent micu by
the said Julius Hermann Guido Wolfram in the Great Seal Patent Office
on the 24th August 1880.
JULIUS HERMANN Guido WOLFRAM, of Dresden, in the Kingdom of Saxony,
Chemist. "IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF COLLODIO-
BROMIDE OF SILVER EMULSION AND PREPARING PHOTOGRAPHIC DRY PLATES
THEREWITH."
This Invention consists in,-
1st. The preparation of a modification of collodio-bromide of silver emulsion
of high sensitiveness by producing the bromide of silver in the presence of a
sufficient quantity of liquor ammonia.
2nd. The preparation of dry plates for photographic purposes by means of
collodio-bromide of silver, the object being to render them as sensitive (or approxi-
mately so) as gelatino-bromide plates. Collodio-bromide of silver emulsion
prepared as heretofore usual, produces photographic dry plates of a very inferior
sensitiveness.
Collodion prepared according to this Invention renders it possible to produce
dry plates for photographic purposes equal (or approximately so) in sensitiveness to
gelatino-bromide of silver plates.
The adding of liquor ammonia to ready made collodio bromide of silver emulsion
and allowing it to react thereon for a considerable period so as to convert the
bromide of silver into its highest state of sensitiveness, does not produce a result so
satisfactory as that obtained by the use of the proparation of gelatino bromide of
silver emulsion. Now I have found that in order to obtain a good result with
collodio bromide of silver, it is essential such bromide of silver should be produced
in the presence of a sufficient quantity of liquor ammonia, and collodio-bromide of
silver emulsion according to my Invention may be prepared in the following
mannor (that is to say):—
I add to 40 to 50 grammes of collodion, which contains 1-3 per cent. of pyroxyline,
a solution consisting of 2 grammes of nitrate of silver dissolved in 8 to 20 grammes
of liquor ammonia, which contains 7 to 9 per cent. of ammonia, and 8 to 20
grammes of absolute alcohol. I further add sufficient alcohol of 40 to 50 per
cent. to re-dissolve all the silver salts that have been precipitated. I then add to
40 to 50 grammes of collodium, which contains 1.3 per cent. of pyroxyline, a
solution consisting of bromide of potassium, of bromide of sodium, or bromide of
ammonium dissolved in 8 to 20 grammes of liquor ammonia, which contains 7 to 9
per cent. of ammonia, to which 8 to 20 grammes of alcohol are added.
This latter solution is added to the first mentioned collodion shaking or agitating
violently at the same time. As soon as a uniform mixture is attained the mixture
of pyroxyline and bromide of silver is precipitated by the addition of a large
quantity of water; the precipitate is then freed from ammonia and salt by
decantation, afterwards dried and dissolves in 50 to 150 grammes of ether alcohol,
to which 1 to 3 per cent. of glycerine and any suitable kind of preservative may
be added.
As a modification of the above described method of preparing the collodio-
bromide of silver, I may use 8 to 20 grammes of liquor ammonia which contain
14 to 18 per cent. of ammonia. In this case I add to 20 to 30 grammes of collodium,
a solution consisting of bromide of potassium, of bromide of sodium, or bromide of
ammonium dissolved in 5 to 10 grammes of water, to which 5 to 10 grammes of
alcohol are added.
The quantity named for nitrate of silver may be varied according to circum-
stances. 2 to 6 grammes of nitrate of silver may be used.
According as the quantity of liquor ammonia is increased the sensitiveness of

page_text: the emulsion will be hightened. Instead of nitrate of silver any other salt of
silver soluble in liquor ammonia may be employed.
It is to be understood that the preparation of collodio-bromide of silver emulsion,
as above, as well as the preparation of dry plates by means of such emulsion can
take place only in a room faintly illuminated by red light..
The dry plates are prepared in the well known manner by pouring unto the
glass plates (which may be previously coated by a weak solution of caoutchouc as
used heretofore) the above described collodio-bromide of silver emulsion, and
hereafter allowing any excess of the poured quantity of the emulsion to drip off
from the plate, or allowing the entire quantity poured to remain on the horizontally
placed plate. The emulsion will soon dry on the plates and coat the same, which
plates are then ready for use. The plates prepared by the collodio bromide of
silver emulsion may, before or after this emulsion has dried, be coated' with any
kind of known preservatives in well known manner.
Having described the nature of my said Invention and explained the manner of
carrying it into practical effect, I would have it understood that what I consider
to be novel and original and therefore claim under the Letters Patent herein before
in part recitod is,-
1. The preparation of a modification of bromide of silver of very high sensi-
tiveness in collodion by the formation of bromide of silver in the presence of
sufficient quantities of liquor ammonia, substantially as described.
2. The preparation of dry plates for photographic purposes by the use of collodio
bromide of silver, substantially as described.
In witness whereof, I, tho said Julius Hermaun Guido Wolfram, have
hereunto set my hand and seal, this Sixteenth day of August, in the year
of our Lord One thousand eight hundred and eighty.
JULIUS HERMANN GUIDO WOLFRAM. (L.S.).