. 15 grains.
Gelatine................................ 46 grains.
Water................................... 163/4 ounces.
After the mixing is completed the perfect separation of the precipitate
takes place in four minutes at most. The clear fluid may be decanted off
almost to the last drop, after which the precipitate is washed three
times with water. In order to dissolve the precipitate pour over it a
solution of 1.5 part of bromide of potassium in 100 parts of water,
agitate, and then add a solution formed of 8 parts of ammonia of the
usual strength in 600 parts of water. The emulsification will begin
at once without any further heating. When now heated on the water
bath--already at from 95 deg. F to 104 deg. F--the whole precipitate will be
suspended, and thin films of the emulsion, when looked through, will
have a grayish tint, but when dry they will appear partially red.
Digestion at 104 deg. F is continued--from half an hour to an hour is
usually long enough--until the film, even when dry, remains violet
through and through. The remaining gelatine, 450 grains dissolved in 16
ounces of warm water, is then added, filtered, and plates coated with
the resultant emulsion.
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