CHEMISTRY GLOSSARY

fluorine    →   fluor

Fluorine was discovered by Henri Moissan (France) in 1886. The origin of the name comes from the Latin word fluere meaning to flow. It is pale yellow to greenish gas, with an irritating pungent odour. Extremely reactive, flammable gas. Reacts violently with many materials. Toxic by inhalation or ingestion. Does not occur uncombined in nature. Fluorine is found in the minerals fluorite (CaF₂) and cryolite (Na₃AlF₆). Electrolysis of hydrofluoric acid (HF) or potassium acid fluoride (KHF₂) is the only practical method of commercial production. Used in refrigerants and other fluorocarbons. Also in toothpaste as sodium fluoride (NaF).

fossil fuel    →   fosilno gorivo

Fossil fuels (coal, oil, and natural gas) are the fuels used by man as a source of energy. They are formed from the remains of living organisms and all have a high carbon or hydrogen content. They have value as fuels on the exothermic oxidation of carbon to form carbon dioxide

and the oxidation of hydrogen to form water

fuel cell    →   gorivi članak

Fuel cell is a device that converts chemical energy into electrical energy. It is different from a battery in that the energy conversion continues as long as fuel and oxidising agent are fed to the fuel cell; that is, in principle indefinitely. (A battery is manufactured with a limited amount of chemicals, and it is exhausted when all the chemicals have reacted.) It is a galvanic cell where spontaneous chemical reactions occur at the electrodes. The fuel is oxidised at the anode, and the oxidising agent (almost always oxygen or air) is reduced at the cathode. Presently, the most commonly used fuel is hydrogen. More conventional fuels (e.g., petrol or natural gas) must be converted (reformed) into hydrogen before they can be utilised in a fuel cell.

Some fuel cells employ an aqueous solution as electrolyte, that can be either acidic or basic (alkaline), or an ion-exchange membrane soaked in aqueous solution can act as the electrolyte. These fuel cells operate at relatively low temperatures (from room temperature to not much above the boiling point of water). Some fuel cells employ molten salts (especially carbonates) as electrolytes and have to operate at temperatures of several hundred degrees centigrade (Celsius). Others employ ionically conductive solids as electrolyte and must operate close to 1 000 °C.

neutral oxide    →   neutralni oksid

Neutral oxides are those oxides which show neither basic nor acidic properties when they react with water. Examples include carbon monoxide (CO) and nitrous oxide (N₂O) which are only slightly soluble in water, and nitric oxide (NO) which is appreciably soluble in cold water.

neutral substance    →   neutralna tvar

Neutral substance is a substance that shows no acid or base properties, has an equal number of hydrogen and hydroxyl ions and does not change the colour of litmus-paper.

neutralisation    →   neutralizacija

Neutralisation is the process in which an acid reacts with a base to form a salt and water.

gadolinium    →   gadolinij

Gadolinium was discovered by Jean de Marignac (France) in 1880. Named after the mineral gadolinite, named for J. Gadolin, a Finnish chemist and mineralogist. It is soft, ductile, silvery-white metal. Reacts slowly with water and oxygen. Dissolves in acids. Metal ignites and burns readily. Gadolinium is found with other rare earths in gadolinite and monazite sand. Used in steel alloying agents and the manufacture of electronic components.

germanium    →   germanij

Germanium was discovered by Clemens Winkler (Germany) in 1886. The origin of the name comes from the Latin word Germania meaning Germany. It is greyish-white semi-metal. Unaffected by alkalis and most (except nitric) acids. Stable in air and water. Germanium is obtained from refining copper, zinc and lead. Widely used in semiconductors. It is a good semiconductor when combined with tiny amounts of phosphorus, arsenic, gallium and antimony.

glass electrode    →   staklena elektroda

Glass electrode is a hydrogen-ion responsive electrode usually consisting of a bulb, or other suitable form, of special glass attached to a stem of high resistance glass complete with internal reference electrode and internal filling solution system. Glass electrode is also available for the measurement of sodium ions.

The glass electrode, which consists of a thin wall glass bulb, has an extremely high electrical resistance. The membrane of a typical glass electrode (with a thickness of 0.03 mm to 0.1 mm) has an electrical resistance of 30 MΩ to 600 MΩ. The surface of a glass membrane must be hydrated before it will function as a pH electrode. When a glass surface is immersed in an aqueous solution then a thin solvated layer (gel layer) is formed on the glass surface in which the glass structure is softer. This applies to both the outside and inside of the glass membrane.

The simplest explanation for the working of the thin glass electrode is that the glass acts as a weak acid (Glass-H).

The hydrogen ion activity of the internal solution is held constant. When a solution of different pH from the inside comes in contact with the outside of the glass membrane, the glass is either deprotonated or protonated relative to the inside of the glass. The difference in pH between solutions inside and outside the thin glass membrane creates electromotive force in proportion to this difference in pH.

nitrate    →   nitrat

Nitrates are all compounds containing radical NO₃^- or any compound containing it, as a salt or ester of nitric acid. Fertilizers consist of sodium nitrate or potassium nitrate.