PRACTICAL PHOTO-MICROGRAPHY. 59 



The following articles are useful : A " Warnerke sensito- 

 meter ;" a so-called "Matchless" gas burner, by which the gas 

 can be lowered out of sight without entire extinction; this 

 will be found vastly convenient in the dark room, Fig. 23. 



FIG. 23. MATCHLESS BURNER. . FIG. 24. SQUEEGEE. 



The following is a list of chemicals which are certain to be 

 required for development and other operations with gelatine- 

 bromide dry plates : 



Pyrogallol 1 ounce 



* Citric acid 1 ounce 



Sodic sulphite, ^ pound ; or potassicmeta bisulphite. 1 ounce 



Sulphurous acid 1 ounce 



Ammonic or potassic bromide 1 ounce 



* Liquor ammonia, sp. gr. .880 (see later) 4 ounces 



Potassic carbonate pure 4 ounces 



* Sodic carbonate (crystals) 4 ounces 



f Sodic hyposulphite 1 pound 



* Potash alum 1 pound 



* Hydrochloric acid (comml. ; useful for cleaning things) 1 pound 



Ammonic carbonate 4 ounces 



Mercuric bichloride (poison) 4 ounces 



For albumen paper printing on " ready sensitized " paper : 



Auric terchloride (" chloride of gold," in sealed tube). 1 tube 

 Sodic acetate, or biborate ("borax ") 1 ounce 



For albumen paper not ready sensitized, in addition to the 

 two last items : 



Argentic nitrate 1 ounce 



Albumenized paper a few quires 



