CHEMISTRY GLOSSARY

ideal gas law    →   jednadžba stanja idealnog plina

The generalized ideal gas law is derived from a combination of the laws of Boyle and Charles. Ideal gas law is the equation of state

which defines an ideal gas, where p is pressure, V molar volume, T temperature, and R the molar gas constant (8.314 JK^-1mol^-1).

indicator    →   indikator

Indicator is a substance used to show the presence of a chemical substance or ion by its colour. Acid-base indicators are compounds, such as phenolphtaleine and methyl orange, which change colour reversibly, depending on whether the solution is acidic or basic. Oxidation-reduction indicators are substances that show a reversible colour change between oxidised and reduced forms.

iodine    →   jod

Iodine was discovered by Bernard Courtois (France) in 1811. The origin of the name comes from the Greek word iodes meaning violet. It is shiny, black, non-metallic solid with characteristic odour. Sublimes easily and as a gas it is violet and intensely irritating to the eyes, nose and throat. Iodine occurs on land and in the sea in sodium and potassium compounds. Required in small amounts by humans. Once used as an antiseptic, but no longer due to its poisonous nature.

ion exchanger    →   ionski izmjenjivač

Ion-exchanger is a solid or liquid material containing ions that are exchangeable with other ions with a like charge that are present in a solution in which the material is insoluble. Ion-exchange resins consist of various copolymers having a cross-linked three-dimensional structure to which ionic groups have been attached.

ionic bond    →   ionska veza

Ionic bond is a strong force of attraction holding atoms together in a molecule or crystal. Typically chemical bonds have energies of about 100 kJ mol^-1. Ionic bond is a bond at which one of the participants, during the procedure of bonding, gives away its unpaired electrons to another atom so that both can achieve electron arrangement of the closest noble gas. In order to form an ionic bond one of the atoms must cross to the positively charged ion by losing certain number of electrons and the other atom must receive those electrons and cross to the negatively charged ion.

ionic strength    →   ionska jakost otopine

Ionic strength (μ or I) is a measure of the total concentration of ions in a solution, defined by

where z_i is the charge of ionic species i and c_i is its concentration.

isoelectric point    →   izoelektrična točka

Isoelectric point (pI or IEP) is the pH of a solution or dispersion at which the net charge on the molecules or colloidal particles is zero. In electrophoresis there is no motion of the particles in an electric field at the isoelectric point. The net charge (the algebraic sum of all the charged groups present) of any amino acid, peptide or protein, will depend upon the pH of the surrounding aqueous environment. For example, alanine can have a charge of +1, 0, or -1, depending on the pH of the solution in which it is dissolved.

isoleucine    →   izoleucin

Isoleucine is hydrophobic amino acids with aliphatic side chain. It is one of the three amino acids having branched hydrocarbon side chains. The side chains of these amino acids are not reactive but, these residues are critically important for ligand binding to proteins, and play central roles in protein stability. Isoleucine is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Ile, I
• IUPAC name: 2-amino-3-methylpentanoic acid
• Molecular formula: C₆H₁₃NO₂
• Molecular weight: 131.12 g/mol

Joule-Thomson coefficient    →   Joule-Thompsonov koeficijent

Joule-Thomson coefficient (μ) is a parameter which describes the temperature change when a gas expands adiabatically through a nozzle from a high pressure to a low pressure region. It is defined by

where H is enthalpy.

Joule-Thomson’s effect    →   Joule-Thomsonov efekt

Temperature of ideal gas will not be changed when it is repressed to a lower pressure, but when real gases are repressed to a lower pressure, a lower or higher temperature change appears under high pressures. The temperature change which appears at real gas expansion in a system into which energy is not brought is called Joule-Thomson’s effect. It was determined that when air is repressed by 1 bar, its temperature drops by 0.25 °C. That minute effect is completely irrelevant for most technical processes, but is also used in gas liquefying procedure.