CHEMISTRY GLOSSARY

chromatography    →   kromatografija

Chromatography is a method of separation of the components of a sample in which the components are distributed between two phases, one of which is stationary while the other moves. In gas chromatography, the gas moves over a liquid or solid stationary phase. In liquid chromatography, the liquid mixture moves through another liquid, a solid, or a gel. The mechanism of separation of components may be adsorption, differential solubility, ion-exchange, permeation, or other mechanisms.

cobalt    →   kobalt

Cobalt was discovered by Georg Brandt (Germany) in 1735. The origin of the name comes from the German word kobald meaning goblin or evil spirit. It is hard, ductile, lustrous bluish-grey metal. Surfaces stable in air. Reacts over time with dilute acids. It has remarkable magnetic properties. Cobalt occurs in compounds with arsenic and sulfur as in cobaltine (CoAsS) and linneite (Co₃S₄). Pure cobalt is obtained as a by-product of refining nickel, copper and iron. Used in many hard alloys; for magnets, ceramics and special glasses. Radioactive cobalt-60 is used in cancer therapy.

explosion    →   eksplozija

Explosion is a rapid violent chemical reaction that produces large amounts of gas and heat, accompanied by light, sound and a high-pressure shock wave.

filter    →   filtar

Filter is a device for separating solid particles from a liquid or a gas. The simplest laboratory filter for liquids is a funnel in which a cone of paper (filter paper) is placed. Special containers with a porous base of sintered glass are also used.

colloid    →   koloid

Colloids are systems in which there are two or more phases, with one (the dispersed phase) distributed in the other (the continuous phase). Moreover, at least one of the phases has small dimensions, in the range between 1 nm and 1 μm (10^-9 m – 10^-6 m). Dimension, rather than the nature of the material, is characteristic. In this size range, the surface area of the particle is large with respect to its volume so that unusual phenomena occur, e.g., the particles do not settle out of the suspension by gravity and are small enough to pass through filter membranes. Macromolecules (proteins and other high polymers) are at the lower limit of this range; the upper limit is usually taken to be the point at which the particles can be resolved in an optical microscope.

Colloidal particles may be gaseous, liquid, or solid, and occur in various types of suspensions:

Sols - dispersions of small solid particles in a liquid.

Emulsions - colloidal systems in which the dispersed and continuous phases are both liquids.

Gels - colloids in which both dispersed and continuous phases have a three-dimensional network throughout the material.

Aerosols - colloidal dispersions of liquid or solid particles in a gas.

Foams - dispersions of gases in liquids or solids.

composition of ocean water    →   sastav oceanske vode

The proportions of the major constituents of ocean water are almost constant throughout the world. Salinity (total salt content) and the concentrations of individual chemical constituents in sea wateris given the units psu (practical salinity units). For most purposes one can assume that the new unit, psu, and the older unit, ‰, are synonymous.

The average composition of the ocean water is as shown on the following table.

flashback    →   uskakanje plamena

Flashback occurs when the flame in a gas torch burns back into the torch or hose; this is often accompanied by a hissing or squealing sound, and a pointed or smoky flame.

fluid mechanics    →   mehanika fluida

Fluid mechanics is the study of various properties of the fluid (liquids and gases): velocity, pressure, density and temperature, as functions of space and time.

fluorescence    →   fluorescencija

Fluorescence is a luminescence phenomenon in which electron returns to it's ground state almost instantaneously (less than 10^-8 second), and in which emission from a luminescent substance ceases when the exciting source is removed. Fluorescence is characterized by radiation emission in all directions.

conditional electrode potential    →   uvjetni elektrodni potencijal

Conditional or formal electrode potential (E°’) is equal to electrode potential (E) when overall concentrations of oxidised and reduced form in all its forms in a solution are equal to one. Conditional electrode potential includes all effects made by reactions that do not take part in the electron exchange, but lead to change of ion power, changes of pH, hydrolysis, complexing, precipitating, etc.

At 298 K (25 °C) and by converting natural (Napierian) logarithms into decimal (common, or Briggian) logarithms, Nernst’s equation for electrode potential can be written as follows: