100 PHOTOGRAPHIC PROCESSES. 



placed in the vulcanite dish, the developer caused to 

 wave to and fro over its surface, till the required 

 density is obtained ; the same precautions as those 

 previously mentioned with regard to fogging, etc., 

 being observed. 



After development the mixed solution is trans- 

 ferred to a separate bottle holding about eight or 

 ten ounces ; when full, this is boiled in an iron sauce- 

 pan for ten minutes, returned to the bottle and 

 securely corked; it will answer admirably for the 

 development of several future plates or paper pic- 

 tures, if always boiled after use, and the clear liquor 

 poured off. 



Fixing and subsequent intensification are pro- 

 ceeded with in exactly the same way as for the 

 other processes. 



The blackening of the plate with ammonia, after 

 whitening with mercury, is carried on in the open 

 air, at all events in another apartment, as it would 

 spoil all subsequent manipulation with the wet plate 

 process. 



It has been recommended to add citric acid to 

 the alum solution when pyro. is used and oxalic acid 

 with ferrous oxalate, to remove any stain due to the 

 developer on the resulting negative. There should 

 be no stain after developing, and we cannot too 

 strongly condemn the use of acids in any of the 

 solutions used subsequent to development. Without 

 entering into the theoretical grounds of this advice, 

 we simply state that nothing tends more, except 

 traces of hypo., to impair the permanency of the 

 negative. 



