Lead tree; Arbor Saturni. Take of sugar of lead, 1 oz.; distilled water, 11⁄2 pint; acetic acid, a few drops; dissolve, place the liquid in a clear white glass bottle, and suspend a piece of zinc in it, by means of a fine thread.
Silver tree; Arbor Dianæ. From nitrate
of silver, 20 gr.; water, 1 fl. oz.; dissolve in a phial, and add about 1⁄2 dr. of pure mercury.
Tin tree; Arbor Jovis. From chloride of tin, 3 dr.; nitric acid, 10 to 15 drops; distilled or rain water, 1 pint; dissolve in a white glass bottle, and hang in it, by a thread, a small rod of zinc.
Obs. In the above experiments the metals are precipitated in a very beautiful arborescent form. It is curious to observe the laminæ shoot out, as it were, from nothing, assuming forms resembling real vegetation. This phenomenon results from voltaic action being set up between the liquid and the metal.
VEGETO-AL′KALI. See Alkaloid.
VEL′LUM. A fine kind of parchment prepared from the skins of calves, kids, and lambs. The skins are limed, shaved, washed, and stretched in hoops or other frames, where they are scraped and trimmed with the currier’s fleshing-knife, and next carefully rubbed down with pumice stone; they are, lastly, polished with finely powdered chalk or fresh-slaked lime, and then dried. A green colour is given with a solution of crystallised verdigris, to which a little cream of tartar and nitric acid has been added; and a blue colour, with a solution of indigo. The surface is often finished off with white of egg, and subsequent friction.
The skins of sheep are commonly used for parchment; those of he-goats and wolves for drum-heads; and those of the ass for battledores. The species of vellum used for church services by binders is said to be prepared from pig-skins. See Pounce.
VEL′VET COLOURS. Syn. Map stains, Paper s.; Lacca fluida, L. Prep. 1. (Blue.)—a. Dissolve litmus in water, and add 1⁄3 of spirit of wine.—b. Dilute Saxon blue or sulphate of indigo with water. If required for delicate work, neutralise the acid with chalk.—c. To an aqueous infusion of litmus add a few drops of vinegar, until it turns of a full blue.
2. (Green.)—a. Dissolve crystallised verdigris in water.—b. Dissolve sap green in water, and add a little alum.—c. Add a little salt of tartar to a blue or purple solution of litmus, until it turns green.—d. Dissolve equal parts of crystallised verdigris and cream of tartar in water.