68 SCIOPTICON MANUAL. 



of white light than from any other cause. A square- 

 sided lantern, having the white glass removed, and yel- 

 low substituted, will be found very convenient; cither 

 gas, a candle, or kerosene can be used for illumination. 



To prevent the collodion film slipping from the plate 

 during the process, it is absolutely necessary that the 

 glass plate should be albumenized. Wash the glass 

 (having previously roughened the edges), drain, and 

 while wet flow over it the following solution : 



Albumen (the white of an egg), .... 1 egg. 



Water, 1 pint. 



Concentrated Ammonia, ....... 10 drops. 



Put the albumen in a clean bottle, then add the water. 

 Shake a little, and add the ammonia; filter through a 

 sponge ; dry in a rack. 



COLLODION. 



Any reliable collodion will answer; it is best to have 

 it quite thick. 'No backing is necessary. 



NEGATIVE BATH. 



Nitrate of Silver, 45 grains. 



Water, 1 ounce. 



Made slightly acid with nitric acid, C.P. Dip the 

 collodionized plate in the bath, and when properly ex- 

 cited, remove the plate, and dip in a bath of pure water ; 

 then wash under a tap with running water. "While wet 

 apply the 



PRESERVATIVE SOLUTION. 



Tannin, 10 grains. 



Gum Arabic, 6 " 



Sugar, 4 



Water, 1 ounce. 



Filter, and add one drachm per ounce of 



Gallic Acid, 24 grains. 



Alcohol, 1 ounce. 



