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° F to 104° 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° 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. But if it be desired to prepare emulsion for storage, wash the precipitate finally with alcohol, and store it either under alcohol or dry it as usual. To use it dissolve in the manner described above and mix with gelatine. The great advantages of this process are evident. Not only is the troublesome washing saved, but, what is more important, the great mass of the gelatine is added to the emulsion in a condition which secures to the film a hitherto unattainable firmness. Also, it enables one to prepare a keeping emulsion with a minimum of alcohol, and, since the quantity of gelatine in the original emulsion is so small, it dries, when it is not desired to keep it under alcohol, so much more rapidly, and thereby also furnishes a more constant preparation.