formaldehyde - Sciencemadness Dot Org

USES OF FORMALDEHYDE 353
High temperature permits short developing times where minimum
processing delay is of paramount importance such as in photographing
the finish of races, x-ray films and films for television transmission. For
obtaining full development in about 10 seconds, Jaenicke 20 recommends
an alkaline-formaldehyde bath between fixation and washing. He also
claims that the addition of very small amounts of aldehydes to the
alkali bath of his split developer reduces the required bathing time considerably.
For ultra-rapid development and fixation requiring no more than
20 seconds for development, fixation and drying of photographic papers,
Fischer 15 hardens the emulsion in 10 per cent formalin solution and develops
in a warm developer containing 25 per cent potassium iodide. Capstaff
10 employs a high-contrast hydroqumone-bisulfite-sodium hydroxideformaldehyde
developer as the "first" developer of his reversal process.
For fixing photographic films, plates, and papers at temperatures up to
90°F, Crabtree 31 recommends a sodium thiosulfate-sodium sulfite-formaldehyde
fixer.
In 1889 Schwartz and Mercklin 38 added fornmldehyde-bisulflte products
to photographic emulsions for increasing the sensitivity of the emulsion.
Subsequent disclosures 7 ' 3 ' 18 * 3 ^ 40 ' 41 recognize that it is common practice to
harden gelatin photographic emulsions with formaldehyde, formaldehydeformers
and derivatives thereof. Merckens 39 points out that a minimum
of gelatin is prerequisite to quick setting of silver-gelatmo-halide emulsions
upon coating, and describes how a 2 per cent gelatin solution treated at
50°C with formaldehyde becomes as viscous as an ordinary solution containing
8-10 per cent gelatin.
Processed photographic films, particularly cinematographic films which
are subject to much wear, are treated with renovating and preserving solutions
containing formaldehyde as an essential ingredient, according to
Bodine 5 , Mackler 38 and Stewart 44 , who also 43 described treating the processed
film with formaldehyde gas. Roth 36 describes a method for rendering
nitrocellulose films fire-proof in ordinary projecting machines by applying a
layer of gelatin to the base side of the film and forming the layer into a
heat-protecting coating by treating it with a mixture of equal parts of a 5
per cent formaldehyde solution and a 2 per cent solution of sodium bisulfite.
Adamson 1 suggests a non-inflammable film support comprising a nucleus
or core of formaldehyde-hardened gelatin containing glycerin as the plasticizer
and coated on both sides with first a rubber varnish and finally a
celluloid varnish.
Formaldehyde is widely used in color photography for hardening the
emulsion layer before treating it with silver, bleaching, mordanting, toning,
etc., 6 ' 9 ' 22 ' 33 - 42 , and in place of alum 26 for toning developed silver images.
Jennings 21 and Schneider 37 prepare aldehyde-condensed dimeric and polymeric
dye-intermediates for use in film emulsions to be processed by color-