34 THE A B C OF PHOTO - MICROGRAPHY 



NO. 2. 



Sodium carbonate, dried and powdered . 2 ozs. 

 " sulphite, . i oz. 



Mix also very thoroughly and put into a 

 similar jar. For developing a photo-micro- 

 graphic negative a single solution is the most 

 convenient and always reliable. For this pur- 

 pose put about 10 grains of No. I in 2 ounces 

 of water and stir until completely dissolved^ 

 then add 20 grains of No. 2 and a few drops 

 of a 10 per cent solution bromide of potas- 

 sium, again stirring thoroughly. To avoid 

 the necessity of weighing the chemicals every 

 time I use two small thimbles, soldered to 

 short pieces of brass wire, one of which holds, 

 when evenly filled, the exact amount of No. i 

 powder; the other doing the same with No. 2. 

 This developer acts slowly but regularly, and 

 should be allowed to proceed until the back 

 of the plate is fairly well darkened, as there is 

 some loss of density in the fixing bath. The 

 addition of a few grains of metol will give 

 greater energy to the developer, but I have 

 not found any other advantage in its employ- 

 ment. The used mixture should not be thrown 

 away, but filtered into a bottle to be used as 

 a restrainer instead of bromide with a freshly 

 made solution. It may be used repeatedly. 



