74

MISCELLANEOUS PROCESSES.

ourselves of this easy method of producing a tolerably sensitive Da-guerreotype paper. Those are, certain irregular formations of oxidesin different states, and the revival of metallic silver in some parts ofthe surface.

I next spread papers with the pure oxide formed by chemical means,and also the protoxide, and many of its salts. These papers were notvery readily affected by iodine, or influenced by light during short ex-posures.

Silver is revived from its solutions by hydrogen gas; consequently,nothing is more easy than by washing a paper with nitrate of silver insolution, to procure a fine silver paper, by passing a current of hydrogengas over it.

A picture of a peculiarly delicate character may bo produced on thiskind of paper; but it has not the required sensibility, and there is agroat want of contrast in the lights and shadows. It may be interest-ing to state, that tho yellow-brown phosphate of silver is as readilyacted on by iodino as the oxides, and is quite as sensitive to luminousinfluence. Phospliuretted hydrogen gas effects the revival of metallicsilver, and the surface produced by means of this gas, used as thohydrogen was in tho former caso, is of a fine steel-blue, which colourarises from a portion of phosphorus having entered into combinationwith the silver. These kinds of paper comported themselves in everyrespect as the metallic tablets—were equally sensitive, and producedpictures as delicately beautiful. Unfortunately, however, owing to thospontaneously inflammablo nature of tho phosphuretted hydrogen gas,it is not safe to operate with it. After various ineffectual contrivancesto overcome this difficulty, I was obliged to abandon the use of this gasentirely—warned of tho danger I incurred, by several violent, but for-tunately, harmless explosions. Tho vapour of phosphorus and of sul-phur was also triod, and many very beautiful effects were produced. Atlength, however, I stopped at sulphuretted hydrogen, which answers inevery respect. *

To preparo this paper, soak a paper of very firm texture, not toomuch glazed, in a weak solution of the muriate of ammonia. It mustthen be wiped with clean cloths, and carefully dried. The paper isthen dipped into a weak solution of tho nitrate of silver, and tho smallbubbles which form on its surface are carefully removed with a camel’shair pencil. When the paper is nearly, but not quite dry, it must boexposed in a closed vessel to sulphuretted hydrogen gas, slowly formedfrom tho sulphuret of antimony and hydrochloric acid; in a few minutesit will become of an iron-brown colour, having a fine metallic lustre.It is again to be passed through a solution of silver, somewhat strongerthan the first, and dried, taking care that no shadow falls on the paperwhilst it is drying. It is then a second time submitted to sulphuration,

* A very interesting account of the revival of gold and silver from their solutions, bythese gases, will be found in a tract on Combustion, published by Mrs. Fulhame.