A New or Improved Process for Removing the Hyposulphites from Photographic Negatives and Prints.
Year: 1897

page_text: Date of Application, 20th May, 1897-Accepted, 26th June, 1897
A New or Improved Process for Removing the Hyposulphites from
Photographic Negatives and Prints.
I PIERRE MERCIER of 23 Rue des Moines Paris, France Pharmaceutical
Chemist 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 :-
Photographic negatives or prints are usually subjected to a final treatment by a
solution of hyposulphite of soda in order to dissolve the argentic salts, which
treatment is termed the fixing, after which they are washed for some time in order
to eliminate the hyposulphites. Such washing often consumes a considerable time
especially when the treatment with hyposulphite of soda has been incomplete, as
the negatives and prints retain in such cases an argentic hyposulphite which is
insoluble in water and withstands the action of ordinary washings.
My invention relates to means for avoiding these long and tedious washings by
the use of solutions prepared with the aid of iodine or iodides, bromine or bromides.
in the following manner that is to say :-
1. I may dissolve in water alkaline iodides such as iodide of potassium or iodide
of sodium. I have discovered that alkaline iodides decompose argentic hypo-
sulphites contained in the negatives or prints as they are withdrawn from the fixing
bath while thus facilitating the washing of the negatives and prints to a far higher
degree than alkaline chlorides such as common salt which had been heretofore
recommended as a dialytic eliminator of hyposulphites.
Instead of using alkaline iodides alone, I may use conjointly with them salts
having an alkaline reaction such as carbonate of soda, sulphite of soda, sodaic
I have
phosphates and the like or an alkali such as potash soda or ammonia.
discovered that the elimination of the hyposulphites is thus more rapid than with
the iodides alone. I often add to the above compounds a small quantity of
common salt which however is not indispensable. As a practical illustration of
the above indications I may use a solution containing about 4 grs. of iodide
of potassium in one litre of water, or I may use the following:
Water
11tre.
I may substitute for the above alkaline iodides alkaline bromides but in such
cases the elimination of the hyposulphites proceeds more slowly.
2. Instead of using alkaline iodides or bromides in the solutions above named,
I may prepare them directly with bromine or iodine which method was the first
employed by ine, the former process having been discovered subsequently after
further experiments.
To prepare the latter solutions I dissolve iodine or bromine in a suitable quantity

page_text: Water
1 litre.
To facilitate the solution of the 3 grs. of iodine I dissolve them previously in
40 grs. of alcohol or thereabouts.
I thus obtain a yellow solution which cannot be used forthwith for it would
corrode the photographic image, it is therefore necessary to wait until it becomes
spontaneously discolored which requires from one or two days or longer or it may
be discolored by heating it for a few minutes or by adding thereto a small
quantity of ammonia, when the solution is discolored and cool it can be utilized
forth with.
Colorless solutions of the kind above described may be obtained by adding a
small quantity of sulphite of soda or by using the latter alone in lieu of the
carbonate of soda, but it is preferable to use the carbonate alone in order to prevent
the introduction of sulphurous compounds in the eliminating means.
To use my solutions the photographic negatives or prints impregnated with the
hyposulphite of the fixing bath are slightly washed with water to remove the
largest portion of its hyposulphites, they are then immersed in one of my solutions
for a short time varying from five minutes to 1 or 2 hours according to
requirements. The negatives or prints may be passed through several similar
baths, if required, the operation being completed by washing them for a few
minutes in clean water.
The efficacy of my process can be readily demonstrated particularly as regards
negatives or prints which have not been left long enough in the fixing bath and
are still impregnated with argentic hyposulphite which is insoluble in water, and
it is easy to ascertain when the negative or print contains no more hyposulphite,
by slightly touching a point of the white parts of the print with a brush previously
dipped in a 10% solution or thereabouts of nitrate of silver when if there be any
byposulphite left there is formed a yellow spot at the said point.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. A process for eliminating the hyposulphites from photographic negatives
and prints after fixing consisting in the treatment of the latter by an aqueous
solution of an alkaline iodide substantially as herein described.
2. A process for eliminating the hyposulphites from photographic negatives and
prints after fixing consisting in the treatment of the latter by an aqueous solution
of an alkaline iodide with a salt having an alkaline reaction substantially as
herein described.
3. A process for eliminating the hyposulphites from photographic negatives and
prints after fixing consisting in the treatment of the latter by an aqueous solution
of an alkaline bromide substantially as herein described.
4. A process for eliminating the hyposulphites from photographic negatives and
prints after fixing consisting in the treatment of the latter by an aqueous solution
of an alkaline bromide with a salt having an alkaline reaction substantially as
herein described.
5. A process for eliminating the hyposulphites from photographic negatives and
prints after fixing consisting in the treatment of the latter by an aqueous solution
of iodine with a suitable alkali or a salt having an alkaline reaction this solution
having to be discolored before use spontaneously, by heat, or by any other means,
substantially as herein described.

page_text: 6. A process for eliminating the byposulphites from photographic negatives and
prints after fixing consisting in the treatment of the latter by an aqueous solution
of bromine with a suitable alkali or a salt having an alkaline reaction this solution
having to be discolored before use spontaneously by heat, or by any other means-
substantially as herein described.
حيمد
1
1008