CHEMISTRY GLOSSARY

marl    →   lapor

Marl is a grey or yellow natural mixture of clay and lime in different proportions. It is also used as a raw material in the production of cement.

molecule    →   molekula

Molecule is the smallest part of a chemical compound that can take part in a chemical reaction. The atoms of a molecule are held together by chemical bonds.

monomer    →   monomer

Monomer is a simple molecule which is capable of combining with a number of like or unlike molecules to form a polymer. Monomer is repeating structure unit within a polymer.

nylon    →   najlon

Nylons are synthetic polyamide fibres that have elastic properties and are used for making textile products and screen mesh.

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(symbol Cl) was defined as the weight of chlorine in grams per kilogram of seawater after the bromides and iodides had been replaced by chlorides.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

copolymer    →   kopolimer

Copolymers are also known as heteropolymers. They are made from two (or more) different monomers, which usually undergo a condensation reaction with the elimination of a simple molecule, such as ammonia or water. A typical example is the condensation of 1,6-diaminohexane (hexamethylenediamine) with hexanedioic acid (adipic acid) to form nylon 6,6.

The properties of a polymeric plastic can most easily be modified if it is a copolymer of two or more different monomers, e.g. acrylonitrile-butadiene-styrene copolymer (ABS). Varying the proportions of the component monomers can preselect its properties.

octane number    →   oktanski broj

Octane number is the assay mark of the liquid motor fuel which shows its anti-knock value. n-heptane, which detonates very easily, has o.n. 0, whereas isooctane, which does not detonate, has o.n. 100. By mixing these hydrocarbons we obtain fuels of different qualities, with values of octane number between 0 and 100.

onyx    →   oniks

Onyx is a semiprecious stone, a type of stone with many different layers of colour.

pigment    →   pigment

Pigments are the substances that give paint colour. Pigments are derived from natural or synthetic materials that have been ground into fine powders. A pigment is different from a dye in that a pigment is insoluble in the media in which it is used.

Pigment is an organic substance found in plant and animal cells that creates colouring.

resonant frequency    →   rezonantna frekvencija

All vibrating systems have one or more resonant frequencies, which depend on system characteristics. If an external force is applied on the system at that frequency, the vibrations will be much greater than at slight different frequencies.