Render sensitive by floating for two or three minutes upon a solution of Nitrate of Silver, 40 grains to the ounce. Thirty grains to the ounce, or less, will be sufficient if the sample be pure; but in that case occasional additions of fresh Nitrate of Silver must be made, as the Bath loses strength.
A second Formula for plain paper.—Take of
| Chloride of Ammonium | 200 | grains. |
| Citrate of Soda[44] | 200 | " |
| Gelatine | 20 | " |
| Water | 20 | fluid ounces. |
[44] This salt may be obtained at the operative chemists; or it may be prepared extemporaneously by neutralizing 112 grains of pure Citric Acid, free from Tartaric Acid, with 133 grains of the dried Bicarbonate or "Sesquicarbonate" of Soda, used for effervescing draughts.
If Towgood's or any English paper be used, the Citric Acid, Carbonate of Soda, and Gelatine may be omitted. With a foreign paper the Citrate tends to give a purple tone to the Positive, when toned by Sel d'or, but the gold toning Bath must be in active order, or the prints will be too red. The Citric Acid also should not be in excess over the alkaline Carbonate.
Render sensitive by floating for three minutes upon a Nitrate Bath of sixty grains to the ounce of water.
Formula III. Ammonio-Nitrate Paper.—This is always prepared without Albumen, which is dissolved by Ammonio-Nitrate of Silver. Take of
| Chloride of Ammonium | 100 | grains. |
| Citrate of Soda | 200 | " |
| Gelatine | 20 | " |
| Water | 20 | fluid ounces. |
Dissolve the Gelatine by the aid of heat; add the other ingredients, and filter. The solution cannot be kept longer than two or three weeks without becoming mouldy. The Saxony paper, or Towgood's English paper, may be employed; the Gelatine and Citrate being retained or omitted, according to the taste of the operator and the mode of toning which is adopted.