Siiv = 28.3

The element silicon (L. silex, silicis, flint, which is nearly all silica = silicon oxide), like boron, resembles carbon. It is infusible, insoluble, non-volatile, and is met with, in crystals as well as amorphous. It occurs mostly as silicon dioxide (silica), SiO2 - agate, amethyst, chalcedony, flint, quartz, rock crystal, sand, but also as silicates, which are silicic acid having its hydrogen replaced by metals - basalt, feldspar, granite, mica, porphyry, etc. Sodium silicate is the chief medicinal compound, although potassium silicate (fusing together potassium carbonate 10 parts, sand 15, charcoal 1) possesses similar properties. Pumice stone, Pumex (same composition as feldspar, obsidian - silica 60-80 p. c. + Al, Ca, Fe, K, Mg, Mn), is a porous, brittle, grayish-white volcanic mineral from Lipari Islands, Grecian Archipelago and Germany; used for abrading, polishing, filtering, tooth powder, etc.

Preparation. - (Unoff.): Liquor Sodii Silicatis, official 1880-1900. - Made by fusing sand or flint 1 part with dried sodium carbonate 2 parts, lixiviating the product with boiling water, filtering, evaporating. It is a semitransparent, yellowish or greenish viscid liquid, odorless, saline, alkaline, sp. gr. 1.350; contains sodium trisilicate and tetrasilicate 33 p. c, nitric acid precipitates silicic hydroxide. Should be kept in well-stoppered bottles.

Properties and Uses. - Sodium silicate arrests organic fermentation and putrefaction. Liquor - deodorant, antiseptic, antiferment, astringent, stimulant; chiefly in surgery for fixing bandages in fractures, coating in erysipelas, like collodion, injection in gonorrhoea, etc.

Terra Silicea Purificata. Purified Siliceous Earth, official. (Syn., Ter. Sil. Purif., Purified Kieselguhr, Purified Infusorial Earth, Diatomaceous Earth, Fossil Flour.)

Manufacture: This form of silica, SiO2, consisting of frustules and fragments of diatoms, is purified by boiling with diluted hydrochloric acid, washing, calcining. It is a very bulky, fine powder, white, pale gray, pale buff, odorless, tasteless; contains 10 p. c. of moisture, but readily absorbs water, retaining 4 times its weight without becoming fluid; insoluble in water, acids, dilute alkaline solutions. Test: 1. Digest 1 Gm. with diluted hydrochloric acid 20 Ml. (Cc.) for 15 minutes, filter, evaporate to dryness 10 Ml. (Cc), incinerate - residue .005 Gm. Impurities: Iron, carbonate, sulphate, moisture, organic substances.

Properties and Uses. - Excipient for pills containing easily reducible ingredients, potassium permanganate, salts of silver and gold; diluent to hygroscopic powders; filtering medium for obtaining sterile filtrates; preparing dynamite, "putz" pomade and other polishes, packing caustic and inflammable substances.

Talcum Puriflcatum. Purified Talc, official. - (Syn., Talc. Purif.; Fr. Talc purifie; Ger. Gereinigter Talk.) Manufacture: Commercial talc (Soapstone, French Chalk), 4MgO.-5SiO2.H2O, is a native hydrous magnesium silicate, sometimes with a small amount of aluminum silicate, etc., from which it should be freed, when for pharmaceutical purposes, by boiling for 15 minutes 500 Gm. with boiling water 2500 Ml. (Cc), gradually adding hydrochloric acid 50 Ml. (Cc), allowing to stand for 15 minutes, decanting, rejecting supernatant liquid (containing the finer particles in suspension), boiling residue in water 2500 Ml. (Cc.) mixed with hydrochloric acid 25 Ml. (Cc), allowing to stand for 15 minutes, rejecting liquid, washing residue by repeated decantation until acidity is removed (no opalescence with silver nitrate T. S.), transferring magma to muslin strainer, draining, drying at 110° C. (230° F.). It is a very fine, white, grayish-white powder, quite free from grittiness, slippery to the touch, adhering to the skin; odorless, tasteless; ignited at red heat - loses 5 p. c Impurities: Iron, aluminum hydroxide, soluble substances.

Preparation. - (Unoff.): Pulvis Talci Compositus, 87 p. c, + boric acid 10, salicylic acid 3.

Properties and Uses. - Chiefly as an aid (medium) in filtering, for which a fineness greater than No. 100 is objectionable, as it passes through the filter requiring frequent pouring back; for dusting powder, the No. 60-80 is superior to the finer bolted varieties; native talc for extracting grease, oil spots, marking cloth (tailors), etc.