Improvements in the Production of Films Sensitive to Light, and of Materials for Assisting or Continuing the Effect of Light on Photographic Films.
Year: 1889

page_text: Date of Application, 15th Jan., 1889
Complete Specification Left. 15th Oct.. 1889-Accepted, 30th Nov., 1889
PROVISIONAL SPECIFICATION.
Improvements in the Production of Films Sensitive to Light, and of
Materials for Assisting or Continuing the Effect of Light on
Photographic Films.
We, ALEXANDER FERDINAND YORK SOHWARTZ, Chemist, and Dr. FRIEDRICH
HERMANN MERCKLIN, Chemist, both of Hanover, in the German Empire, do hereby
declare the nature of our invention to be as follows:-
Our improvements are based on the discovery, that the sensitiveness of silver
compounds is materially increased or that the effect of light on the same is continuod
by the presence of form-aldehyde or of a compound of forin-aldehyde with a bisulphite
of an alkali-metal or of ammonia or of a substituted ammonia (capable of formning
bisulphite) in the sensitive silver compounds.
For photographic purposes these discoveries may be utilized as follows:-
1. By adding one or more of the speciñed compounds, either alone or in mixture
with other substances, at the time of the production of the sensitive film.
2. Or by bathing the finished photographic film in a solution of the said compounds
or mixtures, before the film is exposed to light.
3. Or by treating the photographic film after exposure, with a solution of the said
compounds or mixtures. In this case the changes produced in the film by the action
of the light are continued, so as to obtain in this manner the same result as by a
correspondingly longer exposure to light.
The application of the said compounds constitutes an important progress, because
they possess in an increased measure all advantages of the substances hitherto
employed for similar purposes, without sharing their faults, for instance the tendency
to form clouds or specks.
D: 15th dow of lonery 1880
FAIRFAX & WETTER,
433, Strand, London, Agents.
COMPLETE SPECIFICATION.
Improvements in the Production of Films Sensitive to Light, and of
Materials for Assisting or Continuing the Effect of Light on
Photographic Films.
We, ALEXANDER FERDINAND YORK SCHWARTZ, Chemist, and Dr. FRIEDRICH
HERMANN MEROKLIN, Chemist, both of Hanover, in the German Empire, 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 energetic reducing action of the form-aldehyde may lead to the supposition,
that an alkaline solution of the same would be suitable for developing the latent image
of a photographic film, or for promoting and continuing the decomposition of the
chloride, bromide and iodide molecules commenced by the effect of light; that is to
say, for increasing the sensitiveness of a film treated with the solution, or for intensi-
fying the effect of light after exposure, in such a manner, that the subsequent
development produces a larger reduction of silver, than what would correspond to the
quantity and intensity of the light that has acted on the film.
Experiments have confirmed this supposition, and have furthermore demonstrated,
that the compounds of the form-aldehyde, which may be considered as salts of an
oxymethyl-sulphonic acid, that is, the compounds which are produced by the direct
combination of the form-aldehyde with the acid sulphites of the alkalies, ammonia and
other bases, possess similar properties.

page_text: These last mentioned compounds of the acid sulphites of the alkalies and of ammonia
with the form-aldehyde can easily be produced in a pure condition, but it is difficult,
if not impossible, to produce by this method the compounds of oxymethyl-sulphonic
acid with the other metals and with the organic bases, among which those of silver,
of iron and of the hydroxyl-amine are likewise important from a photographic point of
view.
We have found, however, that the oxymethyl-sulphonic acid itself can be obtained
by admitting sulphurous acid to the so-called crude form-aldehyde or to water which
contains para-form-aldehyde in solution or in suspension.
The sulphurous acid is absorbed in largo quantities, causing a strong development
of heat, and the result is a strongly acid liquid, which dissolves iron, and also zinc,
while energetically developing hydrogen. In the presence of metallic oxides and
carbonates, organic bases and ammonia, this liquid acts like a strong mineral
acid.
In the manner described, it is possible to produce all oxymethyl-sulphonates of the
metals and of the organic bases, by simply causing the acid to act on the metals and
free organic bases, or upon those compounds of metals and of organic bases which are
decomposable by the said acid, while forming the desired salts.
For photographic purposes, the following bodies have been found specially
suitable :-
1. The form-aldehyde and the para-form-aldehyde.
2. The oxymethyl-sulphonates of the alkalies.
3. The ferrous oxymethyl-sulphonate and its double salts with the salts named
under (2).
1. The silver oxymethyl-sulphonate and its combinations with the salts mentioned
under (2).
5. The hydroxyl-amine-oxymethyl-sulphonate.
The discoveries described above are utilized for photographic purposes in the
following manner :-
I. If in the preparation of a photographic film by the emulsion method, silver
oxymethyl-sulphonate (which is also soluble in alcohol) or a compound of the silver-
oxymethyl-sulphonate with the oxymethyl-sulphonate of an alkali or of ammonia, or
the oxymethyl-sulphonate of an alkali or of ammonia, or a mixture of the said bodies,
is added to the finished emulsion, in the proportion of 1 to 2 parts of the said
oxymethyl-sulphonate or mixture to 100 parts of the halogen-silver contained in the
emulsion; or if the said addition is made before the ripening of the emulsion; or if
in the preparation of photographic films by the processes in which the film impreg-
nated with metallic chloride, bromido or iodide, is dipped into a silver bath, we add
silver-oxymethyl-sulphonate, or a double compound of the silver-oxymethyl-sulphonate
with the oxymethyl-sulphonate of an alkali or of ammonia, we obtain photographic films
which are more sensitive to light (oven to weak light), than the films prepared by
the ordinary methods.
II. If an ordinary dry plate is bathed before exposure in a neutral aqueous
solution containing from 01 to 0-2 per cent. of the silver compounds mentioned
under I, for a period of to three minutes, according to its sensitiveness, or in
an equally diluted aqueous and slightly alkaline solution of the form-aldehyde or of
the para-form-aldehyde, or of the oxymethyl-sulphonato of an alkali or of ammonia, or
of a mixture of these salts, and if the plate is then slightly rinsed and again dried, the
photographic results are similar to those obtained if the films have been treated by
method I.
Instead of bathing the dry plate before exposure, it may be bathed after exposure.
Or instead of applying the said compounds in the shape of a special bath, a few drops
of a neutral 1 per cent. solution of the alkali-or of the ammonia-oxymethyl-sulphonate
or of their mixtures, may be added to one of the usual developing mixtures.
III. If the ferrous oxalate developer is prepared by means of the ferrous-oxymethyl-
sulphonate, or better still, by means of the combination of the same with the oxy-
methyl-sulphonate of an alkali or of ammonia, only about a quarter of the usual

page_text: quantity of iron is necessary, in order to obtain equally good results as with the
ordinary iron developer; whereby the durability or stability of the developer is
increased.
IV. The oxymethyl-sulphonate of hydroxyl-amine in alkaline solution gives
excellent results, when used as a developer.
Having now particularly described and ascertained the nature of our said Inven-
tion and in what manner the same is to be performed, we declare that what
we claim is: —
The use of form-aldehyde, or of para-form-aldehyde, or of the compounds of form-
aldehyde (which must be considered as salts of the oxymethyl-sulphonic acid) with an
alkali, ammonia, iron, silver, or of a mixture or combination of the said salts either
alone or in combination with other suitable substances, for the preparation of highly
sensitive photographic films and for the production of chemicals or solutions which
assist or continue the effect of light on photographic films.
A. F. Y. SCHWARTZ,
F. H. MERCKLIN.
By Fairfax
Wetter,
433, Strand, London, Agents.