ELEMENTARY PHOTO-MICROGRAPHY. 49 



B. 



Sodium phosphate ... ... 720 grains 



Caustic soda ... ... 72 



Water ... ... ... 8 ounces 



Four drams of A, four drams of B, and four drams 

 of water are taken, and a few drops of potassium 

 bromide adc^ed if necessary. 



