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Water Glass: WATER GLASS, a water solution containing 20 to 50 percent of dissolved sodium silicate and having a ratio of sodium oxide, Na2O, to silica, SiO:. ranging from 1:1.6 to 1:4. In 1777 the French chemist Baron Louis Bernard Guyton de Morveau (q.v.) melted together quartz and sodium carbonate to make a soluble silicate which was later named "waterglass" by Johann N. von Fuchs, a German chemist and mineralogist. Soluble glass or liquid glass, as water glass is also called, is manufactured by heating sand and sodium carbonate in an open-hearth type furnace.
The seeds should be sown evenly over the compost either by placing large seeds by hand or by gently shaking small seeds from the packet. Cover them by sieving on compost. Fine seeds need a light dusting, larger seeds need proportionately more. Label the pot and water it in by standing the container in a shallow Bath of water Make sure the water does not overflow. After watering stand out to drain. Alternatively water from above, using a watering can with a fine rose. To keep seeds moist and warm, cover with a sheet of glass so that water condenses on the glass and falls back into the compost. To minimize temperature fluctuations, cover the glass with a sheet of paper Place in a warm, dark place.
The resulting sodium silicate is sold in two forms: as a white powder or lumps, formed by shattering the hot melt from the furnace with a stream of cold water and then grinding and screening the fragments; or as water glass, made by dissolving the solid with superheated steam. The density and viscosity of water glass depend on the ratio of sodium oxide to silica, solutions having higher proportions of sodium oxide are thicker than those in which the ratio is low. Viscosity usually ranges from 22° to 69° Baume, the most common being a solution of 40° Baume.Water glass has many uses—to preserve eggs, as a filler in soaps, as sizing for paper, as a component of adhesives and cements, and for weighting silk and fireproofing materials. |
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