CHEMISTRY GLOSSARY

adsorption    →   adsorpcija

Adsorption is a process in which molecules of gas, of dissolved substances in liquids, or of liquids adheres in an extremely thin layer to surfaces of solid bodies with which they are in contact.

aerogel    →   aerogel

Aerogel is a low-density porous transparent material that consists of more than 90 % air. Usually based on metal oxides or silica, aerogels are used as drying agents and insulators.

actinides    →   aktinoidi

Actinides (actinons or actinoids) are the fourteen elements from thorium to lawrencium inclusive, which follow actinium in the periodic table. The position of actinium is somewhat equivocal and, although not itself an actinide, it is often included with them for comparative purpose. The series includes the following elements: thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), amercium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No) and lawrencium (Lr). Every known isotope of the actinide elements is radioactive. Traces of Pa, Np and Pu are consequently found, but only Th and U occur naturally to any useful extent.

activation energy    →   energija aktivacije

Activation energy (E_a) is the energy that must be added to a system in order for a process to occur, even though the process may already be thermodynamically possible. In chemical kinetics, the activation energy is the height of the potential barrier separating the products and reactants. It determines the temperature dependence on the reaction rate.

air curtain    →   zračna zavjesa

Air curtain is a constant stream of bubbles provided by a submerged diffuser (usually a tube type), which surrounds a specified area.

activity    →   aktivitet

Activity (a) is a thermodynamic function used in place of concentration in equilibrium constants for reactions involving nonideal gases and solutions. For the species i activity is defined as

where a_i is the activity of the species i, c_i is its molar concentration, and f_i is a dimensionless quantity called the activity coefficient.

acylaction reaction    →   reakcije aciliranja

Acylaction reaction involves the introduction of an acyl group (RCO-) into a compound. An alkyl halide is reacted with an alcohol or a carboxylic acid anhydride e.g.

The introduction of an acetyl group (CH₃CO-) is acetylation, a process used for protecting -OH groups in organic synthesis.

aldehydes    →   aldehidi

Aldehydes are a broad class of organic compounds having the generic formula RCHO, and characterized by an unsaturated carbonyl group (C=O). They are formed from alcohols by either dehydrogenation or oxidation. Their chemical derivation is indicated by the name al(cohol) + dehyd(rogenation). An example of these distinct aromatic compounds is formaldehyde.

aliphatic compound    →   alifatski spoj

Aliphatic compounds are acyclic or cyclic, saturated or unsaturated carbon compounds, excluding aromatic compounds.

adenosine triphosphate    →   adenozin trifosfat

Adenosine triphosphate (ATP) is nucleotide that is of fundamental importance as a carrier of chemical energy in all living organisms. It consists of adenin linked to D-ribose).