PHOTOGRAPHIC PROCESSES. 99 



the wet process, an impossibility where ammonia is 

 given off, as it contaminates the atmosphere of the 

 dark room. 



The following solutions are used : 



No. I. Neutral Oxalate of Potash, 6 oz. 

 Boiling water, 20 oz. 



Place the oxalate of potash in an earthenware 

 vessel and add the boiling water, stirring with a glass 

 rod till sufficiently cool to be poured into the bottle 

 intended for its reception. If on testing with red 

 litmus paper the solution is found to be alkaline, 

 sufficient dilute sulphuric acid is added to cause a 

 very faint acid reaction with blue litmus paper. If 

 too acid, carbonate of potash may be added to 

 neutralize the excess. The solution is now securely 

 corked. 



No. II. Sulphate of Iron, 3 oz. 

 Distilled Water, 6 oz. 



This solution is also securely corked. 



Suppose we wish to develope a quarter plate; 

 four parts or two drachms of No. I. solution are 

 placed in a glass measure, and one part or \ drachm 

 of No. II. solution is added : not vice versa, or a 

 precipitate of oxalate of iron is formed which weak- 

 ens the mixture. One or two drops, according to 

 circumstances, of the bromide of ammonia solution, 

 the same as that used as a restrainer in alkaline 

 pyro. developer, is added to the whole. The plate is 



H2 



