CHEMISTRY GLOSSARY

chelate    →   kelat

Chelate is a compound characterized by the presence of bonds from two or more bonding sites within the same ligand to a central metal atom. For example, copper complexes with EDTA to form a chelate. Chelate complexes are more stable than complexes with the corresponding monodentate ligands.

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.

Haber, Fritz    →   Haber, Fritz

Fritz Haber (1868-1934) is German physical chemist, winner of the Nobel Prize for Chemistry (1918) for his development of a method of synthesizing ammonia. With Carl Bosch, he invented a process for the large-scale production of ammonia for use in nitrogen fertilizer.

hecto    →   hekto

Hecto, symbol h, is a prefix used in the metric system to denote 100 times. For example, 100 c = 1 hC.

Heusler alloys    →   Heusler legure

Heusler alloys are alloys of manganese, copper, aluminium, nickel, and sometimes other metals which find important uses as permanent magnets.

horse power    →   konjska snaga

Horse power is an obsolete non-SI of power introduced by James Watt in 1782 to allow describing the power of steam machinery. It was equal to the work effort of a horse needed to raise vertically 528 cubic feet of water to one metre in one minute (HP = 735.498750 W).

chlorinity    →   klorinitet

Originally chlorinity (symbol Cl) was defined as the weight of chlorine in grams per kilogram of seawater after the bromides and iodides had been replaced by chlorides. To make the definition independent of atomic weights, chlorinity is now defined as 0.3285233 times the weight of silver equivalent to all the halides.

The Mohr-Knudsen titration method served oceanographers for more than 60 years to determine salinity from chlorinity. This modification of the Mohr method uses special volumetric glassware calibrated directly in chlorinity units. The Mohr method uses potassium chromate (K₂CrO₄) as an indicator in the titration of chloride ions chloride (plus a small amount of bromide and iodide) with a silver nitrate (AgNO₃) standard solution.

The other halides present are similarly precipitated.

A problem in the Mohr titration was that silver nitrate is not well suited for a primary standard. The Danish physicist Martin Knudsen (1871-1949) suggested that a standard seawater (Eau de mer Normale or Copenhagen Normal Water) be created and distributed to oceanographic laboratories throughout the world. This water was then used to standardize the silver nitrate solutions. In this way all chlorinity determinations were referred to one and the same standard which gave great internal consistency.

The relationship between chlorinity Cl and salinity S as set forth in Knudsen's tables is

In 1962, however, a better expression for the relationship between total dissolved salts and chlorinity was found to be

chromium    →   krom

Chromium was discovered by Louis-Nicholas Vauquelin (France) in 1797. The origin of the name comes from the Greek word chroma meaning colour. It is very hard, crystalline, steel-grey metal. The pure metal has a blue-white colour. It is hard, brittle and corrosion-resistant at normal temperatures. Hexavalent compounds toxic by skin contact. The most important chromium mineral is chromite [Fe,Mg(CrO₄)]. Produced commercially by heating its ore in the presence of silicon or aluminium. Used to make stainless steel. It gives the colour to rubies and emeralds. Iron-nickel-chromium alloys in various percentages yield an incredible variety of the most important metals in modern technology.

immersion plating    →   galvaniziranje uranjanjem

Immersion plating involves depositing a metallic coating on a metal immersed in a liquid solution, without the aid of an external electric current. Also called dip plating.

joule    →   džul

Joule (J) is the SI derived unit of energy, work, and heat. The joule is the work done when the point of application of a force of one newton is displaced a distance of one metre in the direction of the force (J = N m). The unit was named after the British scientist James Prescott Joule (1818-1889).