172 Photographic Notes. 
portions unprotected are thus changed to nitro-cellullose, which, by 
brushing, is readily removed in the form of a greenish powder. 
To complete the process, the block is dried, and briskly brushed 
with a stiff brush. The asphalt is lastly removed with benzine, and 
the block is ready for the press. The practical value, as to depth 
and retention of details, we cannot state. It is an innovation, 
however, that may prove worthy of attention.— Pager and Press. 
Toning Blue Ferro-Prussiate Prints.—Prepare a solution 
composed of borax 70 grammes; water I,ooo grammes ; add;,sul- 
phuric acid in small quantities until litmus paper is “slightly 
reddened ; add a few cubic centimetres of ammonia until the 
alkaline reaction again appears, then place in the solution obtained 
ro grammes of crude cachou, and allow to settle, stirring occasion- 
ally. To tonea print, immerse it in this bath for one minute or 
more, according to the tone desired. Wash in several waters, and 
the operation is ended. The prints submitted were toned in a 
cachou bath three months old. The bath had remained exposed 
to the air in a large open vessel. It is, therefore, certain that it 
will keep its qualities for a long time. For richness of tone, these 
prints are comparable to the best albumen prints. This result had 
never before been obtained.—PauL Roy, in Progrés Photographique. 
Converting a Print made on Eastman Paper into a Plati- 
notype.—After development, fix, wash, and place the print face 
downwards in :— 
Chloro-platinate of Potash ... 15 grains 
Distilled Water 5 ... 34 fluid ounces 
Chlorhydric Acid, pure ... 3 fluid drachms 
The print should remain twenty minutes in this bath, then be 
rapidly washed and placed in a solution of chloride of copper. By 
this operation the silver is converted into chloride of silver, and 
acquires a brown tint. Should the tone be too weak, it may be 
strengthened with the oxalate developing bath. All these opera- 
tions may be made in diffused light. Wash well for fifteen min- 
utes, then dry.—-Aonzteur. 
To Detect Hyposulphite of Soda.—A simple test for ascer- 
taining when the hypo. is eliminated, consists in adding to the 
washing water in which the prints are immersed, a small quantity 
of an alcoholic solution of iodine, the effect of this being to change 
the white back of each print to a light blue colour, which proves 
that hypo. is still present as the paper. The prints are continued 
to be washed until the blue disappears from the back of the print, 
and it is then known that the hypo. is completely eliminated. 
