Saltpetre — Saltpetre is a popular name for potassium nitrate.
Salts — Salts are formed by the replacement of acidic hydrogen by a metal or radical by the reaction of an acid upon an alakli.
Samarium — Samarium is an element with the symbol Sm.
Scandium — Scandium is a metal element with the symbol Sc.
Selenium — Selenium is a rare metal element with the symbol Se. It was discovered in 1817 by Berzelius in the refuse of a sulphuric acid manufactory in Sweden.
Silicate — A silicate (sillic acid) is a compound formed by the combining of silica (SiO2) and water in various proportions.
Silurian — The Silurian was the fifth geological period, 335,000,000 years ago. This period marked the appearance of the first land plants.
Silver-steel — Silver-steel is an alloy of one part silver and 500 parts Silver-steels first made around 1822 and was adopted by the cutlers of Sheffield, England for making fine razors, surgical instruments etc.
Sintered — see "Sintering"
Sintering — Sintering is the process of heating strongly a quantity of more or less amorphous material, so causing it to coalesce into a single solid mass.
Slag — Slag is the chemical compound resulting during the smelting of metallic ores. It results because of the action of the flux on impurities in the ore.
Slaked Lime — Slaked Lime is a popular name for calcium hydroxide, Ca(OH)2. Which is obtained by slaking calcium oxide. It is an important constituent of mortar and cement.
Slaking — Slaking is a chemical term for mixing a substance with water, as in the process of slaking lime to create slaked lime.
Soda — Soda is a common name for sodium carbonate (Na2CO3).
Soda ash — see "Sodium carbonate"
Soda Water — see "Aerated water"
Sodagrain — Sodagrain is a tradename for caustic soda.
Sodium amide — Sodium amide is a white, crystalline, water-soluble flammable powder used in the manufacture of sodium cyanide and in organic synthesis.
Sodium arsenite — Sodium arsenite is a white or greyish-white, water-soluble, poisonous powder used as a weed-killer and as an insecticide.
Sodium Bisulphite — Sodium Bisulphite is a salt of Sulphurous Acid.
Sodium Carbonate — Sodium carbonate (soda ash) is an anhydrous, greyish-white, odourless, water-soluble powder. It is used in the manufacture of glass, ceramics, soap, paper and petroleum products.
Sodium cyanide — Sodium cyanide is a white, crystalline, deliquescent powder. It is soluble in water and very poisonous. It is prepared by heating sodium amide with charcoal and is used in casehardening alloys and electroplating.
Sodium fluoride — Sodium fluoride is a colourless, crystalline, water-soluble poisonous substance used as an insecticide, rodenticide and also as a source of fluoride in toothpaste and added to water in many developed countries.
Sodium Hydrate — Sodium Hydrate (caustic soda) is a white, opaque, brittle substance with a fibrous texture. It readily dissolves in water and was formerly used in the manufacture of soap.
Sodium Hydroxide — Sodium hydroxide is a brittle, white, deliquescent solid with a soapy feel. It dissolves in water to give a strongly alkaline solution and is widely used in the manufacture of soaps, detergents, cellulose and rayon.
Sodium Iodide — Sodium iodide is a salt found in kemp. It forms anhydrous cube crystals which are very soluble in water and alcohol.
Sodium Nitrate — Sodium Nitrate is the deliquescent salt (NaNO3) occurring naturally as caliche, or made by the reaction of nitric acid and soda ash. It is used as a fertilizer and in the manufacture of explosives.
Sodium Stearate — Sodium stearate is used as the basis of soap and detergents and is used in the manufacture of toothpaste.
Sodium Sulphite — Sodium Sulphite is a salt of Sulphurous Acid. It has the formulae Na2SO37H2O.
Sodium thiosulphate — Sodium thiosulphate (hypo) is a white, crystalline, water-soluble substance used in photography as a fixing agent.
Soil — Soil is a loose covering of broken rocky material and decaying organic matter.
Solid — A solid is a substance in which the molecules do not have free movement.
Solution — A solution is a homogeneous mixture of substances that cannot be separated by mechanical means.
Stalactite — A stalactite is a mass of calcareous matter hanging in caves, formed by the filtration of water containing calcium bicarbonate in solution through holes or pores in the cave roof. the evaporation of the water and carbonic acid gas leaves behind it a deposit of limestone which continues to increase in size so long as the water drops.
Stalagmite — A stalagmite is similar to a stalactite, but grows upwards from the cave floor, usually below a stalactite.
Steel — Steel is an alloy of iron and carbon.
Sterling silver — Sterling silver is an alloy of silver and copper.
Stone Age — Stone Age is the name in anthropology for the period of human culture before the discovery and use of metal when man made his tools and weapons mainly of flint, but sometimes of other stones, and later of bone, horn and ivory or wood.
Stratified — see "Stratum"
Stratosphere — The stratosphere is that region of the upper atmosphere where the temperature ceases to fall with increasing height above the earth's surface, and either remains constant or slightly increases.
Stratum — Stratum is a geological term describing a mass of sedimentary rock (a strata) of great horizontal extent, which was deposited more or less continuously on the bottom of former seas or lakes, or sometimes on the surface of flat plains or deserts. Stratified rocks are mostly sandstones, shales and limestone.
Strontium — Strontium is a metal element with the symbol Sr of the alkaline-earth group.
Sulphuric Acid — Sulphuric acid has the formulae H2SO4.
Sulphurous Acid — Sulphurous Acid (H2SO3) is a solution of sulphur dioxide in water.
Superphosphate — Superphosphate is a manure made by mixing calcium hydrogen phosphate with gypsum.
Symbol — The "symbol" used to denote those metals and minerals found in the Periodic Chart of Elements. Consists of one or two letters. These symbols are used in writing chemical formulas.