Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1854 edition. Excerpt: ... II.--TALBOTYPE; OB, PHOTOGRAPHY ON PAPER. COMPOUNDS OF SILVER. If Oxide Of Silver (Ag,0) precipitated from a solution of the nitrate, is exposed for several hours to the solar rays, the parts exposed to the light acquire a deeper olive tint than the covered parts. If the exposure is continued a week or longer, it is found that the deep olive color turns lighter again, and that the covered parts are much darker than the exposed parts. I have frequently had occasion to observe that oxide of silver spread on paper, acquired a much lighter tint after a few days' exposure to light.* Nitrate Of Silver, (AgO, NOs).--This salt, if absolutely pure, is not perceptibly affected by light, neither in the solid state nor in solution; but in nitrate of silver containing the least admixture of organic matter, the influence of light speedily produces an alteration. This property induced Sir John Herschel, in his first photographic experiments, to put organic substances on the paper which he intended to operate upon, and to imbue it then with solution of nitrate of silver; however, he did not obtain the desired result. But since that time it has been found that the joint application of organic substances with the silver salt, serves to promote and heighten to an extraordinary degree the alteration which the latter suffers under the influence of light. Count Rumford found that nitrate of silver, mixed with charcoal or with a carbonated earth, suffered reduction to the metallic state under the influence of the solar rays. Prismatic Analysis. -- The color which the prismatic spectrum produces on paper prepared with nitrate of silver, is first a light brown, which changes slowly to a deeper tint; the part under the blue ray acquires a bluish brown color, that..
