CHEMISTRY GLOSSARY

bronze    →   bronca

Bronze is an alloy made primarily of copper and tin. It may contain as much as 25 % tin. Bronzes with 10 % or more tin are harder, stronger, and resistant to corrosion. As bronze weathers, a brown or green film forms on the surface. This film inhibits corrosion. Silicon or aluminium is often added to bronze to improve resistance to corrosion. Phosphorus, lead, zinc, and other metals may be added for special purposes. The alloy is hard and easily cast and is extensively used in bearings, valves and other machine parts.

Bronze was one of the first alloys developed by ancient metal workers. The Bronze Age occurred in Europe around 2200 to 700 BC. Bronze was used for weapons such as spearheads, swords, and knives. Since ancient times, bronze has been the most popular metal for casting statues and other art objects.

The term bronze has been adopted commercially for many copper-rich alloys that contain little or no tin but are similar in colour to bronze, including aluminium bronze, manganese bronze, and silicon bronze. Aluminium bronze is used to make tools and, because it will not spark when struck. Manganese bronze is actually a brass that contains manganese. It is often used to make ship propellers because it is strong and resists corrosion by sea water.

freezing    →   smrzavanje

Freezing is the change of a liquid into a solid state as the temperature decreases. For water, the freezing point is 0 °C (or 273.16 K).

gel    →   gel

Gels are colloids in which both dispersed and continuous phases have a three-dimensional network throughout the material, so that it forms a jelly-like mass (e.g. gelatine). One component may sometimes be removed to leave a rigid gel (e.g. heating silica gel).

Buchner flask    →   Buchnerova tikvica

Büchner flask (also known as a vacuum flask, filter flask, side-arm flask or Kitasato flask) is a thick-walled Erlenmeyer flask with a side arm to which a vacuum can be applied.

Bunsen burner    →   Bunsenov plamenik

Bunsen burner is a standard source of heat in the laboratory. German chemist Roberts Bunsen (1811-1899) improved the burner's design, which had been invented by Faraday, to aid his endeavors in spectroscopy. The Bunsen burner has a vertical metal tube through which a fine jet of fuel gas is directed. Air is drawn in through airholes near the base of the tube and the mixture is ignited and burns at the tube’s upper opening. The flow of this air is controlled by an adjustable collar on the side of the metal tube. When the whole is closed a yellow safety flame is displayed. Where as when the whole is open it displays a power dull blue flame with a faint blue outer flame with a vibrant blue core used u for combustion and hearting. The flame can reach temperatures of 1 500 °C.

caesium    →   cezij

Caesium was discovered by Robert Bunsen and Gustav Kirchhoff (Germany) in 1860. The origin of the name comes from the Latin word caesius meaning sky blue or heavenly blue. It is very soft, light grey, ductile metal. Reacts readily with oxygen. Reacts explosively with water. Caesium is found in pollucite [(Cs₄Al₄Si₉O₂₆)·H₂O] and as trace in lepidolite. Used as a ’getter’ to remove air traces in vacuum and cathode-ray tubes. Also used in producing photoelectric devices and atomic clocks. Since it ionises readily, it is used as an ion rocket motor propellant.

calcium    →   kalcij

Calcium was discovered by Sir Humphry Davy (England) in 1808. The origin of the name comes from the Latin word calix meaning lime. It is fairly hard, silvery-white metal. Exposed surfaces form oxides and nitrides. Reacts with water and oxygen. Occurs only in compounds. Calcium is obtained from minerals like chalk, limestone and marble. Pure metal is produced by replacing the calcium in lime (CaCO₃) with aluminium in hot, low pressure retorts. Used by many forms of life to make shells and bones. Virtually no use for the pure metal, however two of its compounds are, lime (CaO) and gypsum (CaSO₄), are in great demand by a number of industries.

glacial acetic acid    →   ledena octena kiselina

Glacial acetic acid (CH₃COOH) is the pure compound, as distinguished from the usual water solutions known as acetic acid. It is a colorless liquid or crystalline substance (melting point 16.6 °C) with a pungent, vinegar odor.

honey    →   med

Honey is a sweet, amber colored, viscous fluid produced by honeybees from the nectar of flowers. It is composed primarily of fructose (about 40 %), glucose (about 35 %), and water (up to 20 %). In addition, honey contains sucrose, maltose, trisaccharides, and small amounts of minerals, vitamins, and enzymes.

calomel electrode    →   kalomel elektroda

Calomel electrode is a type of half cell in which the electrode is mercury coated with calomel (Hg₂Cl₂) and the electrolyte is a solution of potassium chloride and saturated calomel. In the calomel half cell the overall reaction is

Table: Dependence of potential of calomel electrode upon temperature and concentration of KCl according to standard hydrogen electrode