Gilding, by immersion

Dissolve teroxide or terchloride of gold in a solution of pyrophosphate of soda, and dip the article to be gilt in it.

Electro -Gilding, by Elkington's patent process, is thus performed: - A solution of 5 oz. of gold (see Acid, Nitro-hydrochloric, further back) is prepared, and boiled till it ceases to give out yellow vapours: the clear solution is mixed with 4 gallons of water, 20 lbs. of bicarbonate of potash added, and the whole boiled for 2 hours. The articles, properly cleaned, are suspended on wires, and moved about in the liquid from a few seconds to a minute, then washed, dried, and coloured in the usual way,

The solution used in gilding with the voltaic apparatus is made by dissolving 1/4 oz. of oxide of gold, with 2 oz. of cyanide of potassium, in a pint of distilled water.

Ginger Beer

See Beverages.

Purgative Ginger Bread

See further back.

Glass of Borax

Calcine boras with a strong heat till the water of crystallization is expelled, and the salt fuses into a clear glass.

Soluble Glass

Mix 10 parts of carbonate of potash, 15 of quartz (or of sand free from iron and alumina), and 1 part of charcoal. Fuse together. The mass is soluble in 4 or 5 parts of water; and the filtered solution evaporated to dryness yields a transparent glass, permanent in the air. - Fuchs.

Glass

Glass differs considerably in composition, owing to the purposes for which it is intended; but it may be said to consist mainly of mixtures, in varying proportions, of silicates of potash, soda, lime, baryta, magnesia, alumina, and lead, coloured by the addition of small quantities of different metallic oxide, particularly those of iron, manganese, cobalt, uranium, and gold. Crown glass and green bottle glass contain a portion of lime. Green glass and some kinds of foreign white glass are free from lead, and should therefore be selected for chemical uses.

Toughened Glass

M. de la Bastie's process for toughening glass, consists in raising it to a very high temperature, and then plunging it while hot into a heated oleaginous bath. The process can only be successfully carried out by attention to a number of minute details.

How To Clean Glass

The vessel to be cleansed is filled, or if large, rinsed with a moderately dilute solution of the permanganate of potash, contact being prolonged till a film of hydrated manganic oxide has been deposited; the solution is then poured away, and the glass vessel rinsed with some strong hydrochloric acid.

Glazes

Common earthenware is glazed with a composition containing lead, on which account it is unfit for many pharmaceutical purposes. The following glaze has been proposed, among others, as a substitute: - 100 parts of washed sand, 80 of purified potash, 10 of nitre, and 20 of slaked lime; all well mixed and heated in a blacklead crucible, in a reverberatory furnace, till the mass flows into a clear glass. It is then to be reduced to powder. The goods to be slightly burnt, placed under water, and sprinkled with the powder.