| Water | 2¼ | ounces. |
| Nitrate of silver | 75 | grains. |
Dissolve (in a 4-ounce vial) the nitrate of silver in the water, and then pour one-fourth of the solution into an ounce graduate or any convenient vessel: this keep for farther use in preventing the presence of an excess of ammonia. Now, into the bottle containing the three-fourths put about 4 drops of aqua-ammonia; shake well and a brown precipitate will be given. Continue adding the ammonia, drop by drop, and shake after each addition, until the brown precipitate is re-dissolved and the solution is clear; then pour back into the bottle the one-fourth taken out at first: this will leave the solution slightly turbid, and when so, there is no excess of ammonia which would be objectionable. It may now be filtered through filtering paper, and it (the clear liquid) is ready for use. This should be kept in the dark, as it decomposes rapidly when exposed to light.
The method of silvering the paper with ammonio-nitrate of silver, is as follows: take a tuft of clean cotton, roll it into a ball-shape, then wet it by holding it against the mouth of the bottle containing the ammonio-nitrate, and when well wet, apply it to the paper (which should be placed flat on a clean board) by gently rubbing it over the surface, care being taken not to roughen it.
If the solution has not been filtered for some time, it would be advisable to pour a little on the centre of the paper, and then distribute it over the surface by means of the cotton, which is held in the fingers: by this last method any sediment which may be in the bottom of the bottle is prevented from getting upon the paper, and causing spots.
I have used a brush for the purpose of distributing the solution, by which plan there is less liability of getting it on the fingers and staining them. Care must be taken to cover the entire surface of the paper, or there will be light streaks, occasioned by the absence of the silvering solution.
This want of silver will appear on the paper in light parts, as seen in the accompanying cut:
Fig. 36.