CHEMISTRY GLOSSARY

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.

plutonium    →   plutonij

Plutonium was discovered by Glenn T. Seaborg, Edwin M. McMillan, J. W. Kennedy and A. C. Wahl (USA) in 1940. Named after the planet Pluto. It is silvery-white, extremely radioactive artificially produced metal. Reacts with oxygen and acids; resists alkalis. Attacked by steam. Highly toxic. Plutonium is found rarely in some uranium ores. Made by bombarding uranium with neutrons. Used in bombs and reactors. Small quantities are used in thermo-electric generators.

poison    →   otrov

Poisons are substance, which upon contact or being introduced into an organism, impair or prevent normal metabolic processes from taking place, thus altering the normal functioning of organs or tissues.

Poisons are molecules or material that tends to collect on a catalyst surface, blocking access to active sites or destroying their activities.

Poisons are substance that can reduce a nuclear reaction by absorbing neutrons, thereby preventing more fission. If enough poisons are present in a reactor core, the chain reaction will die out.

polar molecule    →   polarna molekula

Polar molecules are molecules at which centres of gravity of positive and negative charge are not in the same point.

polarimeter    →   polarimetar

Polarimeter is an appliance which measures the angle of turning of polarisation light.

polarimetry    →   polarimetrija

Polarimetry measures the overall turning of the flat of polarised light. It is used when analysing optically active substances and compounds.

polarogram    →   polarogram

Polarogram is a graph of current versus potential in a polarographic analysis. The position of a polarographic wave in a polarogram along the x axis (E_1/2) provides an identity of the substance while the magnitude of the limiting diffusion current (i_d) provides the concentration of this substance.

vapour pressure    →   tlak pare

Vapour pressure is the pressure of a gas in equilibrium with a liquid (or, in some usage, a solid) at a specified temperature.