A Textbook of Chemistry for Nurses

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1919. Not illustrated. Excerpt: ... quartz, smoky quartz, milky quartz, or amethyst, named from their color. Agate is mostly petrified wood in-which silica has slowly replaced the cellular structure of the tree, preserving the rings of growth more or less perfectly and showing different colors as different foreign matter has been introduced from time to time. A very large number of rocks are silicates, such as the felspars, kaolin, the clays, etc. 2. Water Glass.--Silica is not soluble in water or any of the common acids; but when fused with sodium carbonate it reacts as shown by the equation: Si02 + Na2C03-» Na2Si03 + C02 Sodium silicate thus prepared is a nearly colorless, flintlike looking compound, with few uses. If instead of boiling dry to obtain the solid, it is left in the form of a solution, as is usually done, it has about the consistency of glycerine, and if pure not specially different in appearance. It is thus sold under the name of water glass and has manifold uses. For the manufacture of paper boxes and in many similar places where glue was formerly used, water glass is now being substituted, being cheaper. It is also used as a cementing material in many ways; and mixed with nine parts of water it is recommended as a preservative for eggs. The solution is poured into a jar and the eggs added as obtained. They should be covered by the solution and the jar kept covered to avoid excessive evaporation. It is probably the best method known of preserving eggs, as they will keep reasonably well for nine to twelve months. The solution fills the pores of the shell and prevents germs causing decomposition from entering. 3. Window Glass.--This is a cheap variety of glass formed by fusing together lime, sodium carbonate and silica. The resulting product is a sodium calcium silicate, not so...