CHEMISTRY GLOSSARY

heavy water    →   teška voda

Water molecules are composed of two hydrogen atoms and one oxygen atom (H₂O). If the hydrogen atoms of a water molecule are replaced by deuterium atoms, the result is heavy water (D₂O). Deuterium differs from hydrogen by having one neutron in the nucleus of the atom. There is approx. one part in 5000 D₂O in normal water and it can be concentrated by electrolysis. Heavy water has a higher boiling point (101.4 °C) and melts at 3.6 °C. Heavy water is 20/18=1.11 times heavier than ordinary water.

hypsometric curve    →   hipsometrijska krivulja

Hypsometric curve (or hypsographic curve) shows the distribution of height of a given area (on land) and depth (at sea). The term originates from the Greek word hypsos meaning height. The part of the curve that reflects the cross section of the ocean bottom is called the bathygraphic curve.

Horizontal dashed lines indicate average height of the continents at 840 meters above sea level, and average depth of the oceans at 3 682.2 meters below sea level. If all the land above sea level (green) was moved into the sea (blue), the oceans would still be 3 km deep.

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).

manganese    →   mangan

Manganese was discovered by Johann Gahn (Sweden) in 1774. The origin of the name comes from the Latin word magnes meaning magnet, or magnesia nigri meaning black magnesia (MnO₂). It is hard, brittle, grey-white metal with a pinkish tinge. Impure forms are reactive. Rusts like iron in moist air. Manganese is most abundant ores are pyrolusite (MnO₂), psilomelane [(Ba,H₂O)₂Mn₅O₁₀] and rhodochrosite (MnCO₃). Pure metal produced by mixing MnO₂ with powered Al and ignited in a furnace. Used in steel, batteries and ceramics. The steel in railroad tracks can contain as much as 1.2 % manganese. It is crucial to the effectiveness of vitamin B₁.

nerve poison    →   živčani bojni otrov

Nerve poison (nerve gas, agents) have had an entirely dominant role since the Second World War. Nerve poisons acquired their name because they affect the transmission of nerve impulses in the nervous system. All nerve poisons belong chemically to the group of organo-phosphorus compounds. They are stable and easily dispersed, highly toxic and have rapid effects both when absorbed through the skin and via respiration. Nerve poisons can be manufactured by means of fairly simple chemical techniques. The raw materials are inexpensive and generally readily available.

The most important nerve agents included in modern chemical weapons arsenals are:

Nerve poisons are colorless, odorless, tasteless liquids of low volatility. Antidotes are atropine sulfate and pralidoxime iodide.

perfect crystal    →   savršeni kristal

Perfect crystal is a crystal with no defects or impurities made of completely identical repeating subunits. Further, a perfect crystal has only one possible arrangement of subunits, with every subunit making exactly the same contribution to the total energy of the crystal.

transmittance    →   transmitancija

Transmittance (τ) is the ratio of the radiant or luminous flux at a given wavelength that is transmitted to that of the incident radiation. Also called transmission factor.

normal conditions    →   normalni uvjeti

Gas is under normal (or standard) conditions when: p₀ = 10⁵ Pa and T₀ = 273.15 K (0 °C). IUPAC recommends that the former use of the pressure of 1 atm as standard pressure (equivalent to 101 325 Pa) should be discontinued. At these conditions, the molar volume of gas V_m0 is 0.022 711 m³ (22.711 L).

osmotic pressure    →   osmotski tlak

Osmotic pressure (Π) is the excess pressure necessary to maintain osmotic equilibrium between a solution and a pure solvent separated by a membrane permeable only to the solvent. In an ideal dilute solution

where c_B is the amount-of-substance concentration of the solute, R is the molar gas constant, and T the temperature.

Ostwald’s dilution law    →   Ostwaldov zakon razrjeđenja

Ostwald’s dilution law is a relation for the concentration dependence of the molar conductivity Λ of an electrolyte solution, viz.

where c is the solute concentration, K_c is the equilibrium constant for dissociation of the solute, and L₀ is the conductivity at cΛ = 0. The law was first put forward by the German chemist Wilhelm Ostwald (1853-1932).