CHEMISTRY GLOSSARY

krypton    →   kripton

Krypton was discovered by Sir William Ramsay and Morris W. Travers (England) in 1898. The origin of the name comes from the Greek word kryptos meaning hidden. It is colourless, odourless rare noble gas. Reacts only with fluorine. Krypton is obtained from production of liquid air. Used in lighting products. Some is used as inert filler-gas in incandescent bulbs. Some is mixed with argon in fluorescent lamps. The most important use is in flashing stroboscopic lamps that outline airport runways.

mass spectrometry    →   masena spectrometrija

Mass spectrometry is an analytical technique in which ions are separated according to the mass/charge (m/e) ratio and detected by a suitable detector.

In a mass spectrometer a sample is ionised and the positive ions produced are accelerated into a high-vacuum region containing electric and magnetic fields. These fields deflect and focus the ions onto a detector. A mass spectrum is thus obtained, consisting of a series of peaks of variable intensity to which m/e values can be assigned. Different molecules can be identified by their characteristic pattern of lines.

nuclear reactor    →   nuklearni reaktor

Nuclear reactor is an assembly of fissionable material (uranium-235 or plutonium-239) designed to produce a sustained and controllable chain reaction for the generation of electric power.

The essential components of a nuclear reactor are:

1. The core, metal rods containing enough fissionable material to maintain a chain reaction at the necessary power level (as much as 50 t of uranium may be required).
2. A source of neutrons to initiate the reaction (such as a mixture of polonium and beryllium)
3. A moderator to reduce the energy of fast neutrons for more efficient fission (material such as graphite, beryllium, heavy water, and light water are used)
4. A coolant to remove the fission-generated heat (water, sodium, helium, and nitrogen may be used)
5. A control system such as rods of boron or cadmium that have high capture cross sections (to absorb neutrons)
6. Adequate shielding, remote-control equipment, and appropriate instrumentation are essential for personnel safety and efficient operation.

Onsager relations    →   Onsagerove relacije

Onsager relations are an important set of equations in the thermodynamics of irreversible processes. They express the symmetry between the transport coefficients describing reciprocal processes in systems with a linear dependence of flux (J_i) on driving forces (X_j).

In Onsager’s theory the coupling coefficients are equal, L_ij = L_ji. This is known as reciprocal relations. The theory was developed by the Norwegian chemist Lars Onsager (1903-1976) in 1931.

ozone    →   ozon

Ozone is an alotropic form of oxygen. It is an unstable blue gas with a pungent odour. It is a powerful oxidising agent. The gas is made by passing oxygen through a silent electric discharge.

palladium    →   paladij

Palladium was discovered by William Hyde Wollaston (England) in 1803. Named after the asteroid Pallas which was discovered at about the same time and from the Greek name Pallas, goddess of wisdom. It is soft, malleable, ductile, silvery-white metal. Resists corrosion; dissolves in oxidizing acids. Absorbs hydrogen. Metal dust is combustible. Palladium is obtained with platinum, nickel, copper and mercury ores. Used as a substitute for silver in dental items and jewellery. The pure metal is used as the delicate mainsprings in analog wristwatches. Also used in surgical instruments and as catalyst.

phosphorus    →   fosfor

Phosphorus was discovered by Hennig Brandt (Germany) in 1669. The origin of the name comes from the Greek word phosphoros meaning bringer of light. White phosphorus is white to yellow soft, waxy phosphorescent solid with acrid fumes. Toxic by inhalation, ingestion, or skin contact. Red phosphorus is powdery, non-flammable and non-toxic. Phosphorus is found most often in phosphate rock. Pure form is obtained by heating a mixture of phosphate rock, coke and silica to about 1450 °C. Used in the production of fertilizers and detergents. Some is used in fireworks, safety matches and incendiary weapons. Phosphorus is also important in the production of steels, phosphor bronze and many other products.

plasma    →   plazma

Plasma is a highly ionised gas in which the charge of the electrons is balanced by the charge of the positive ions, so that the system as a whole is electrically neutral. Plasmas are created by exposing gases at low pressure to an electric or electromagnetic field. In semiconductor processing, plasmas are used for etching and thin film deposition (the excited state of the gas makes it very reactive). In everyday life plasmas are used to give light in fluorescent light bulbs, neon lamps, and blue insect traps.

plastic    →   plastika

Plastic is a material that can be shaped by the application of heat or pressure. Most are based on synthetic polymers although some are the product of natural substances (such as cellulose derivatives, but excluding the rubbers.). They are usually light and permanent solids, being also heat and electric isolators. If the materials soften again when reheated, they are said to be thermoplastic. If, after fashioning, they resist further applications of heat, they are said to be thermoset.

platinum    →   platina

Platinum was discovered by Antonio de Ulloa (South America) in 1735. The origin of the name comes from the Spanish word platina meaning silver. It is rare, very heavy, soft, silvery-white metal. Resists oxygen and water. Platinum is produced from deposits of native, or elemental. Used in jewellery, to make crucible and special containers and as a catalyst. Used with cobalt to produce very strong magnets. Also to make standard weights and measures. Resists corrosion and acid attacks except aqua regia.