CHEMISTRY GLOSSARY

sand    →   pijesak

Sand is loose particles of hard, broken rock or minerals, with a diameter of between 0.02 mm and 2 mm. Sand is the most common form of silica used in making glass.

Acheson process    →   Achesonov proces

Acheson process is an industrial process to synthesize graphite and silicon carbide (carborundum), named after its inventor the American chemist Edward Goodrich Acheson (1856-1931). In this process, a solid-state reaction between pure silica sand (SiO₂) and petroleum coke (C) at very high temperature (more than 2500 °C) leads to the formation of silicon carbide under the general reaction:

While studying the effects of high temperature on carborundum, Acheson had found that silicon vaporizes at about 4150 °C, leaving behind graphitic carbon.

diamond    →   dijamant

Diamond is the hardest known mineral (with a hardness of 10 on Mohs’ scale). It is an allotropic form of pure carbon that has crystallised in the cubic system, usually as octahedral or cubes, under great pressure. Diamond crystals my be colourless and transparent or yellow, brown or black. They are highly prized as gemstones, but also have extensive uses in industry, mainly for cutting and grinding tools. Diamonds occur in ancient volcanic pipes of kimberlite, or in river deposits that have been derived from weathered kimberlite. Industrial diamonds are being increasingly synthetically produced.

sedimentary rocks    →   sedimentne stijene

Sedimentary Rocks are formed by the accumulation and subsequent consolidation of sediments into various types of rock. There are three major types of sedimentary rocks:

Biogenic sedimentary rocks are formed from organic processes when organisms use materials dissolved in water to build a shell or other skeletal structure.

Clastic sedimentary rocks are composed directly of the sediments or fragments from other rocks.

Chemical sedimentary rocks are formed through evaporation of a chemical rich solution.

Based on their sizes, sediment particles are classified, based on their size, into six general categories:

• boulder (>256 mm)
• cobble (64 - 256 mm)
• gravel (2 - 64 mm)
• sand (1/16 - 2 mm)
• silt (1/256 - 1/16 mm)
• clay (<1/256 mm)

silicon    →   silicij

Silicon was discovered by Jöns Jacob Berzelius (Sweden) in 1824. The origin of the name comes from the Latin word silicis meaning flint. Amorphous form of silicon is brown powder; crystalline form has grey metallic appearance. Solid form unreactive with oxygen, water and most acids. Dissolves in hot alkali. Silica dust is a moderately toxic acute irritant. Silicon makes up major portion of clay, granite, quartz and sand. Commercial production depends on a reaction between sand (SiO₂) and carbon at a temperature of around 2200 °C. Used in glass as silicon dioxide (SiO₂). Silicon carbide (SiC) is one of the hardest substances known and used in polishing. Also the crystalline form is used in semiconductors.

thorium    →   torij

Thorium was discovered by Jöns Jakob Berzelius (Sweden) in 1828. Named after Thor, the mythological Scandinavian god of war. It is heavy, grey, soft, malleable, ductile, radioactive metal. Tarnishes in air; reacts with water. Reacts violently with oxidants. Thorium is found in various minerals like monazite and thorite. Used in making strong alloys. Also in ultraviolet photoelectric cells. It is a common ingredient in high-quality lenses. Bombarded with neutrons make uranium-233, a nuclear fuel.