Ammonium sulpbocyanide, 10-20gr.; water, 500cc. (15 1/2 oz.).

The gold solution is now added to the above, when a red precipitate will occur, which, however, redissolves in a few days. When perfectly clear, the solution is ripe and ready for use; 55 cc. (1 1/2 oz.)of it put into 5 parts of water will tone one sheet of 18 x 22 paper. If the sulphocyanide solution is made strong, the tones will be warmer; if weak, then they will become more violet or blue. An old bath used several times produces fine sepia tones.

After toning, the print is slightly rinsed, and is then immersed for 10 minutes in an alkaline fresh fixing bath: - Soda hyposulphite, 1 oz.; water, 30 oz.

The bath may be made alkaline by the addition of a little ammonia.

After fixing, the prints should be washed for 3 hours in several changes of water.

Owing to the delicate character of the collodion film, and its liability to be defaced, it is necessary that the greatest care be exercised in the manipulation of the paper.

Liesegang has suggested the application of this collodion film to wood, porcelain, etc, in the following manner: - First, a sheet of smooth gummed commercial paper is flowed with the emulsion, as previously described, the print is made, but not toned and fixed. It is then transferred from the paper to any desired support. The wood, porcelain, etc, on which the print is to be transferred is previously coated with a thin film of gelatine. The print - in a wet condition - is now squeegeed-on to the porcelain, or other support, and the whole is soaked in water at the ordinary temperature for 5 minutes, or until the gum coating between the collodion film and paper softens sufficiently to allow the paper to be easily pulled off. We then have a transparent film left on the porcelain. The picture is toned, fixed, and washed on its new support in the usual manner.

A reversed position will be given to the picture, but this will be of no consequence when it is used as a transparency or a lantern slide. - (S. C. Passavant.) (See also iv. 378.)