Page:Various Forces of Matter.djvu/191

Rh ($22$) Page 100. Paper prepared like gun cotton. It should be bibulous paper, and must be soaked for ten minutes in a mixture of ten parts by measure of oil of vitriol with five parts of strong fuming nitric acid. The paper must afterwards be thoroughly washed with warm distilled water and then carefully dried at a gentle heat. The paper is then saturated with chlorate of strontia, or chlorate of baryta, or nitrate of copper, by immersion in a warm solution of these salts. (See Chemical News Vol. I. page 36.)

LECTURE VI.

($23$) Page 145. Sulphindigotic acid. A mixture of one part of indigo and fifteen parts of concentrated oil of vitriol. It is bleached on the side at which hydrogen gas is evolved in consequence of the liberated hydrogen withdrawing oxygen from the indigo, thereby forming a colourless deoxidised indigo. In making the experiment, only enough of the sulphindigotic acid must be added to give the water a decided blue colour.

($24$) Page 147. Lead tree. To make a lead tree, pass a bundle of brass wires through the cork of a bottle, and fasten a plate of zinc round them just as they issue from the cork, so that the zinc may be in contact with every one of the wires. Make the wires to diverge so as to form a sort of cone, and having filled the bottle quite full of a solution of sugar of lead, insert the wires and cork and seal it down, so as to perfectly exclude the air. In a short time the metallic lead will begin to crystalise around the divergent wires, and form a beautiful object.

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