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Bromide Paper
Ferrous sulphate Sulphuric acid Distilled water
III. Bromide of ammonium ... ... ... 480 grs.
Distilled water         ... ......... 30 ozs.
To make the developer, add one part of solution of ferrous sulphate to six parts of oxalate solution, and a few drops of solution of bromide as a restrainer. In mixing the developer it is essential that the solution of iron be added to the oxalate, and not the reverse, or a thick yellow precipitate of ferrous oxalate will be formed. It is advisable to use distilled water for all solutions, or a precipitate of oxalate of lime will be formed, and the solution will be clouded, and both the oxalate and ferrous sulphate solutions should be distinctly acid to test paper. Another formula which we have used with success is the following: -
One Solution Formula.
Neutral oxalate of potash              ......2,600 grs.
Citric acid ... .., ... ...... 100 ..
Ferrous sulphate ... ...... ... 975 ,,
Boiling distilled water ... ... ... 20 ozs.
Dissolve the oxalate in the water, and add the citric acid, and finally the ferrous sulphate; stir till the whole of the latter is dissolved, and a deep orange yellow solution is formed. For use one part of this solution is diluted with three parts of water, or preferably with the same quantity of the following solution, when it will be about equal in strength to that made by the first formula. The solution may be kept good for months in the syphon bottle (Fig. 11), described under Atmospheric Action.
Solution for Diluting Concentrated Developer.
Neutral oxalate of potash......... 120 grs.
Distilled water         ... ......... 4 ozs.
Another formula for a one-solution developer, which was suggested by Carey Lea, the well-known American scientist, is as follows : - .
Neutral oxalate of potash ... ... ... 1,600 grs.
Distilled water         ...         ..         ...... 10 ozs.