CHEMISTRY GLOSSARY

polymerization    →   polimerizacija

Polymerization is a reaction of connecting many monomers in one long molecule whereby polymers are created.

polystyrene    →   polistiren

Polystyrene is a vinyl polymer. Structurally, it is a long hydrocarbon chain, with a phenyl group attached to every other carbon atom. Polystyrene is produced by free radical vinyl polymerization, from the monomer styrene. Polystyrene or Styrofoam is used in the construction industry as insulating material and for production of containers.

polyvinyl chloride    →   polivinil klorid

Poly(vinyl chloride) or the PVC is hard and resistant homopolymer produced by the polymerization of the gas vinyl chloride [CH₂CHCl]. The pure polymer is hard, brittle and difficult to process, but it becomes flexible when plasticizers are added. After mixing with plasticizers, stabilizers, and pigments, the resin may be fabricated by techniques such as calendering, molding, or extrusion into flexible articles such as raincoats, shower curtains, and packaging films. The resin is not plasticized for use in making rigid products such as water pipe, plumbing fittings, and phonograph records.

potassium    →   kalij

Potassium was discovered by Sir Humphry Davy (England) in 1807. The origin of the name comes from the Arabic word qali meaning alkali (the origin of the symbol K comes from the Latin word kalium). It is soft, waxy, silver-white metal. Fresh surface has silvery sheen. Quickly forms dull oxide coating on exposure to air. Reacts strongly with water. Reacts with water to give off flammable gas. Reacts violently with oxidants. Occurs only in compounds. Potassium is found in minerals like carnallite [(KMgCl₃)·6H₂O] and sylvite (KCL). Pure metal is produced by the reaction of hot potassium chloride and sodium vapours in a special retort. Used as potash in making glass and soap. Also as saltpetre, potassium nitrate (KNO₃) to make explosives and to colour fireworks in mauve. Vital to function of nerve and muscle tissues.

Prandtl number    →   Prandtlova značajka

Prandtl number (Pr) is a dimensionless quantity used in fluid mechanics, defined by

where η is viscosity, ρ is density, and a is thermal diffusivity.

Rayleigh number    →   Rayleighova značajka

Rayleigh number (Ra) is a dimensionless quantity used in fluid mechanics, defined by

where l is length, g is acceleration of gravity, α is cubic expansion coefficient, T is temperature, ρ is density, η is viscosity, and a is thermal diffusivity.

refractometer    →   refraktometar

Refractometer is an optical device used from measurement of refractive index. A refractometer takes advantage of the fact that light bends as it passes through different materials. It can be used to measure the salinity of water or the amount of sugar in fresh grapes. Refractometers are available with or without automatic temperature compensation (ATC).

When using a conventional saltwater refractometer, a sample is placed on an optical prism in the sample window. As light shines through the sample, it is bent according to the salinity of the water, and casts a shadow on the scale that is visible through the eyepiece. Salinity is read directly through the eyepiece.

Reynolds number    →   Reynoldsova značajka

Reynolds number (Re) is a dimensionless quantity used in fluid mechanics, defined by

where ρ is density, v is velocity, l is length, and η is viscosity.

rubidium    →   rubidij

Rubidium was discovered by Robert Bunsen and Gustav Kirchhoff (Germany) in 1861. The origin of the name comes from the Latin word rubidius meaning dark red or deepest red. It is soft, silvery-white, highly reactive metal. Ignites in air. Reacts violently with water or oxidants. Rubidium occurs abundantly, but so widespread that production is limited. Usually obtained from lithium production. Used as a catalyst, photocells and vacuum and cathode-ray tubes.

Schmidt number    →   Schmidtova značajka

Schmidt number (Sc) is a dimensionless quantity used in fluid mechanics, defined by

where η is viscosity, ρ is density, and D is diffusion coefficient.