148 PRACTICAL PHOTO-MICROGRAPHY. 



of the silver bath, as the latter is more and more nearly satur- 

 ated with the collodion solvents of the immersed plates, the 

 more alcohol will be required. A fresh silver bath requires 

 little or no alcohol in the developer. 



FERROUS SULPHATE DEVELOPER. 



Proto-sulphate of iron, fresh green crystals 15 grains 



Nitric acid 1 minim 



Water 1 ounce 



Alcohol q. s. 



AMMONIO-SULPHATE DEVELOPER (FROM " PROCESSES"). 



Ammonio-sulphate of iron 77 grains 



Acetic acid (glacial) 70 minims 



Water Bounces 



Alcohol q. s. 



One or other of these developing solutions is deftly swept 

 over the plate from a cup, and no harm will be done with the 

 iron developers if a little solution should run over the edge of 

 the plate. The iron acts more rapidly than the pyro developer, 

 and the latter should be carefully watched and instantly rejected 

 if it shows signs of turbidity. In each case the solution is to be 

 kept moving over the plate until the image has gained consid- 

 erable strength, but none of the solutions is to be poured on 

 and off the plate. As we do not approve of re-development 

 for slide making, we advise that the developer be allowed to 

 act fully, provided no muddiness appears. The plate is now 

 washed, and fixed with 



Or, 



Potassic cyanide 20 grains 



Water. . . 1 ounce 



Sodi'c hyposulphite 100 grains 



Water 1 ounce 



We prefer the cyanide, but it is a dangerous poison, the 

 handiest antidote in case of accidental imbibition being a good 

 draught of the iron developer. After fixing, the plate is to 

 be well washed, particularly after hypo. 



Frequently the slide at this stage wants " pluck." The remedy 

 is intensification, but the remedy must be applied with caution. 



