The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Gelatine Emulsions
Gelatino-Chloride
slowly stirring in some more" of the sulphate, almost any desired proportion of the original gelatine may be precipitated. If only about half is precipitated, almost all the gum-like deterioration products are left behind. The clot is best freed from traces of sulphate of soda by being finely divided, and soaked in repeated changes of ice-cold water, in which a small proportion of salicylic acid, or some other antiseptic, is dissolved. Gelatine purified in this way is very useful in connection with some of the bichromate processes, but gelatine thus purified is perhaps more especially valuable in preparing lantern plates for development, as in a case of this kind it is specially important to ensure the absence of any trace of such fog, or general reduction of the silver, as may result from the use of deteriorated gelatine. The sulphate of soda does not affect the ultimate solubility of the precipitated gelatine in water.
Gelatine Emulsions. See Emulsion.
Gelatino-Chloride Emulsion Paper. This is an outcome of collodio-chloride emulsion paper, which was known in England as Simpson-type ; just as gelatine took the place of collodion for plates, so gelatine replaced the collodion for this purpose, J. B. Obernetter, of Munich, being among the first to make the gelatino-chloride emulsion paper. The following formulae will be found all that can be desired.
No. I.
Gelatine ... ...        ...        ... ...    230 grs.
Distilled water ...        ...        ... ...        6 drms.
Soak for an hour and dissolve  by the  aid of a gentle heat, and add
Nitrate of silver ...        ... ......        6 grs.
To this mixture add gradually
Lithium chloride ...        ...        ... ...        1 gr.
Tartaric acid... ...        ...        ... ...        1 ,,
Distilled water ...        ...        ... ...        1 drm.
No. II.
Nelson's soft gelatine         ...        ...        ...     139 grs.
Heinrich's hard gelatine ...        ...        ...    293 ,,
Ammonium chloride           ...        ...        ...    540 ,,
Distilled water        ... ...        ...        ...    100 drms.
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