No. 2 for Blacker Tones.
Citric acid ............... 60 grs.
Potassium chloroplatinite ... ... ... 2 ,,
Distilled water ...... ... ... 2 ozs.
Not much guide as to the final tone of the print is to be obtained by examining them by transmitted light. After toning the prints should be well washed, and then passed into solution of carbonate of soda, about 1 oz. to the pint, and thence into the fixing bath.
Playertype. A process for direct copying which appears to depend on some unrecognised principle. A sheet of sensitive development paper is laid face downwards on a print - as an engraving in a book - pressed in contact, and the back of the paper is exposed to light, when, if the exposure was correct, a developable image is obtained. (See The Amateur Photographer, Nov. 13th, 1896, p. 398.)
Plumbago Process. See Powder Process.
Pneumatic Holder. A convenient apparatus for holding plates for the purpose of coating, used chiefly in the old col-lodion days, the pressure of the atmosphere keeping the plate in its position on the holder.
Poisons. Some of the chemicals used in photographic pro-cesses are poisonous when taken internally or when absorbed through the skin. Aqueous hydrofluoric acid when applied to the skin, even in a dilute state, causes painful ulcers, and 1 in 80 can also cause irritation and tenderness. Bichromate of potash and cyanide of potash, when applied to cuts, wounds, and abrasions, are absorbed, and may cause much mischief, and even fatal results. The subjoined table is not given to encourage hasty and often ill-judged treatment, but it may give useful hints when medical aid is not obtainable. A special caution may be needed against giving strong acids or alkalies as antidotes ; indeed, unprofessional treatment should seldom go beyond emollients, and such an emetic as mustard and hot water.