The Art and Practice of Silver Printing

salt in solution. The first point to consider is the strength of the solution. If we float albumenized paper (face downwards) on a solution of 10 grains of silver nitrate to the ounce of water,

ion we have been experimenting with is too small. The water dissolves the albumen first, and then the silver has time to act upon it to form the insoluble albuminate. If we soak paper in com

an equal mixture of the two more chloride would be formed than albuminate; in other words, that the ammon

r nitrate is necessary to prevent the

ss active by holding some other soluble matter in its embraces. This is usually effected by adding some other neutral and inactive nitrates. There does not seem to be any theoretical limit to the a

f. How are we to fix the strength of t

e extract a passage from an

is much slower in formation than the chloride, and has less affinity for the silver. If the silver solution be not sufficiently strong, the chloride may rob that portion of it with which it is in contact of all the silver before any (or, at all events, sufficient) albuminate has been formed, the molecule being composed almost entirely

will follow. Immediately the paper is placed in contact with the solution, silver chloride is formed, and the amount of the silver nitrate in the layer of fluid in immediate contact with the surface being scarcely diminished by the formation of silver chloride, the albuminate is formed almost

turating both the albumen and the salt with silver, the time of flotation must be pro

film, and then the formation of the albuminate would proceed nearly equally throughout the whole of the interior. Evidently, then, in this case, the contact of the silver solution would be less prolonged than in the former case. If the floating be prolonged the silver solution in the interior will become

thus su

a strong solution may

n a weak solution re

he ounce of silver according to the amount of soluble chloride dissolved in the alb

d, after thoroughly soaking, should be decanted off, and added to the other spirit. The spirit containing the chloride may then be placed in a glass vessel standing in hot water, when it will evaporate and leave the chloride behind. It may be weighed; but since it is better to know how much silver chloride (AgCl) would be formed, the residue should be dissolved in a few drops of water,

best strength of silver nitrate solution for sensitizing, and a fair

he amount of silver abstracted from the whole is also equal, which reduces the strength per ounce more with the former than with the latter. A weak sensitizing solution, therefore, requires much more attention th

clean bottle, and add half-a-pint of water to it, and shake it to dissolve it. The best water for the purpose is distilled water; but filtered rain, pure spring, or river water answers well. If the water contain any chlorides, it will be shown by a milkiness due to a formation of silver chloride. This must be filtered out when the remaining pint and a-half of water is added. The solution i

al Sol

r nitrate

r 1

ed Sol

r nitrate

ate or sodium

r 1

from water. When very dry, the liberated chlorine (see page 32) is apt to attack the albuminate, whereas it is deprived of much of its

liberated chlorine would scarcely be able to attack even the silver. Moisture, though very little, is desirable. In the excessively dry climate of In

llowed to be acid with nitric acid, since t

is. The reason why nitric acid is to be avoided is shown by placing a print in dilute nitric acid. It is well known that darkened silver chloride is unaffected by it; but the print will be found to change colour, and to become duller and

surface of the albumen; but the ordinary explanation of its effect is defective. If a solution of common alum be added to the silver nitra

ns of adding it as recommended by some writers. When filtering the solution, put a small lump of alum in the fi