CHEMISTRY GLOSSARY

sediment    →   sediment

1. Sediment is a fragmental material that originates from weathering of rocks and is transported by, suspended in, or deposited by water or air or is accumulated in beds by other natural agencies. When solidified, sediments form sedimentary rocks.

2. Strictly, sediment is a solid material that has settled down from a state of suspension in a liquid.

sedimentation    →   sedimentiranje

Sedimentation is a process of separating specifically heavier, suspended matter, than the solution is. Solid matter settles on the bottom of the vessel and the liquid above it is poured off. The settling zone is the largest portion of the sedimentation basin. This zone provides the calm area necessary for the suspended particles to settle. The sludge zone, located at the bottom of the tank, provides a storage area for the sludge before it is removed for additional treatment or disposal.

sol    →   sol

Sols are dispersions of small solid particles in a liquid. The particles may be macromolecules or may be clusters of small molecules. Lyophobic sols are those in which there is no affinity between the dispersed phase and the liquid (e.g. silver chloride dispersed in water). Lyophobic sols are inherently unstable, in time the particles aggregate, and form a precipitate. Lyiophilic sols, on the other hand, are more like true solutions in which the solute molecules are large and have an affinity for the solvent (e.g. starch in water). Association colloids are systems in which the dispersed phase consists of clusters of molecules that have lyophobic and lyophilic parts (e.g. soap in water).

solubility    →   topljivost

Solubility is the maximum amount of solute that dissolves in a given quantity of solvent at a specific temperature. Generally, for a solid in a liquid, solubility increases with temperature; for a gas, solubility decreases. Common measures of solubility include the mass of solute per unit mass of solution (mass fraction), mole fraction of solute, molality, molarity, and others.

state of matter    →   agregatno stanje

State of matter is one of the tree physical states in which matter can exist, i.e. solid, liquid or gas. Plasma is sometimes regarded as the fourth state of matter. By means of heating a solid substance will cross to liquid state at its melting point. If we heat up a liquid and beyond, at its boiling point it will cross to gaseous state - vapour.

styrene    →   stiren

Styrene is an unsaturated hydrocarbon (C₆H₅OC₂H₃O) colourless, toxic liquid with a strong aromatic aroma. It is soluble in alcohol, ether, acetone, and carbon disulfide, but dissolves only slightly in water. It is used to make plastics such as polystyrene, ABS, styrene-butadiene rubber styrene-butadiene latex and unsaturated polyesters.

supercritical fluid    →   superkritični fluid

Supercritical fluid is any substance above its critical temperature and critical pressure (see phase diagram). It shows unique properties that are different from those of either gases or liquids under standard conditions. A supercritical fluid has both the gaseous property of being able to penetrate anything, and the liquid property of being able to dissolve materials into their components. Solublity increases with increasing density (i.e. with increasing pressure). An example of this is naphthalene which is practically insoluble in low pressure carbon dioxide. At 100 bar the solubility is 10 g/L and at 200 bar it is 50 g/L. Rapid expansion of supercritical solutions leads to precipitation of a finely divided solid.

supercritical fluid chromatography    →   superkritična fluidna kromatografija

Supercritical fluid chromatography (SFC) is a hybrid of gas and liquid chromatography. SFC is of importance because it permits the separation and determination of a group of compounds that are not conveniently handled by either gas or liquid chromatography. These compounds are either nonvolatile or thermally labile so that gas chromatography cannot be used and they do not contain functional groups that make possible detection by liquid chromatography. SFC has been applied to a wide variety of materials including natural prodcuts, drugs, foods, pesticides and herbicides, fossil fuels, explosives and propellants.

superfluid helium    →   superfluidni helij

Superfluidity in helium-4 was discovered in 1938 by the Soviet physicist Pyotr Leonidovich Kapitsa. Helium-4 exhibits superfluidity when it is cooled below 2.18 K (-270.97 C), which is called the lambda (λ) point. At these temperatures, helium-4 exhibits the characteristics of two distinct fluids, one of which appears to flow without friction. An extensive series of experiments showed that in this state of helium, called helium II (He II), there is an apparent enormous rise in heat conductivity, at an increase rate of about three million. Another unusual property of He II is its mobile, rapid flow through capillaries or over the rim of its containment vessel as a thin film that exhibits no measurable viscosity and appears unaffected by the forces of gravity or evaporation and condensation.

tantalum    →   tantal

Tantalum was discovered by Anders Ekeberg (Sweden) in 1802. The origin of the name comes from the Greek word Tantalos meaning father of Niobe in Greek mythology, (tantalum is closely related to niobium in the periodic table). It is rare, grey, heavy, hard but ductile, metal with a high melting point. Exposed surfaces form corrosion resistant oxide film. Attacked by HF and fused alkalis. Metal ignites in air. Tantalum always found with niobium. Chiefly occurs in the mineral tantalite. Often used as an economical substitute for platinum. Tantalum pentoxide is used in capacitors and in camera lenses to increase refracting power. It and its alloys are corrosion and wear resistant so it is used to make surgical and dental tools.