ELEMENTARY PHOTO -MICROGRAPHY. 127 



Most plate makers give instructions for cold 

 and warm tones that may be obtained by simple 

 development, adopting normal exposure and 

 developer for cool tones, and longer exposure and 

 weaker developer with more liberal use of restrainer 

 for warm tones ; but outside this limited range 

 recourse must be had to chemical baths for any 

 special portion of the spectrum. 



The following methods of treatment will give 

 a varied field of choice, and yield results in accord- 

 ance with the wish of the operator. The quantities 

 given are for two or three slides only, but any 

 number may be treated by a proportionate in- 

 crease in the volume of the bath. Commence 

 always with the slide in a dry state. 



Bhie-black and Purple. 

 Sulphocyanide ammonium . 6 grains. 

 Water . . . . . . 2 ounces. 



Gold chloride . . . . J grain. 



Immerse until the desired tone is reached, then 

 wash and dry. 



Red and Copper. 



A. 



Potassium ferricyanide . . ij grains 

 Water . . . . . . . i ounces. 



B. 



Uranium nitrate . . . . 3 grains. 

 Ammonium sulphocyanide . 15 



