CHEMISTRY GLOSSARY

gasoline    →   motorni benzin

Gasoline is a complex mixture of volatile hydrocarbons that may have between 5 to 12 carbons. The major components are branched-chain paraffins, cycloparaffins, and aromatics. Gasoline is most often produced by the fractional distillation of crude oil as the fraction of hydrocarbons in petroleum boiling between 30 °C and 200 °C. The quality of a fuel is measured with its octane number. Octane number is the measure of the resistance of gasoline against detonation or preignition of the fuel in the engine. The higher the octane number, the more compression the fuel can withstand before detonating. The octane number is determined by comparing the characteristics of a gasoline to isooctane with good knocking properties (octane number of 100) and heptane with bad (octane number of 0).

saponification    →   saponifikacija

Saponification is a proces of hydrolysis of esters using hot sodium hydroxide solution to produce the salt of a carboxylic acid. Saponification usually refers to the hydrolysis of esters of fatty acids to manufacture soaps.

selenide    →   selenid

Selenides are compounds having the structure R-Se-R (R not equal to H). They are thus selenium analogues of ethers. Also used for metal salts of H₂Se.

hydrolysis    →   hidroliza

Hydrolysis is a chemical reaction in which water reacts with another substance to form two or more new substances. This involves ionisation of the water molecule, as well as splitting of the compound hydrolysed, e.g.

Examples are conversion of starch to glucose by water in the presence of suitable catalysts and a reaction of the ions of a dissolved salt to form various products, such as acids, complex ions, etc.

iridium    →   iridij

Iridium was discovered by Smithson Tennant (England) in 1803. The origin of the name comes from the Latin word iris, meaning rainbow, because its salts are highly colored. It is heavy, brittle, white metal. Unreactive in air, water and acids. Attacked by fused NaOH. Metal ignites and burns readily. Iridium is found in gravel deposits with platinum. Used with osmium to tip gold pen points, to make crucible and special containers. Also to make alloys used for standard weights and measures and heat-resistant alloys. Also as hardening agent for platinum.

Kohlrausch’s law    →   Kohlrauschov zakon

Kohlrausch’s law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations. If a salt is dissolved in water, the conductivity of the solution is the sum of the conductances of the anions and cations. The law, which depends on the independent migration of ions, was deduced experimentally by the German chemist Friedrich Kohlrausch (1840-1910).

neodymium    →   neodimij

Neodymium was discovered by Carl F. Auer von Welsbach (Austria) in 1885. The origin of the name comes from the Greek words neos didymos meaning new twin. It is silvery-white, rare-earth metal that oxidizes easily in air. Reacts slowly in cold water, more rapidly as heated. Metal ignites and burns readily. Neodymium is made from electrolysis of its halide salts, which are made from monazite sand. Used in making artificial ruby for lasers. Also in ceramics and for a special lens with praseodymium. Also to produce bright purple glass and special glass that filters infrared radiation. Misch metal, used in the manufacture of pyrophoric alloys for cigarette lighters, contains about 18 % neodymium metal. (Typically composition of misch metal are Ce:Nd:Pr:La:Other rare earth=50:18:6:22:4). Neodymium is used to create some of the most powerful permanent magnets on Earth, known as NIB magnets they consist of neodymium, iron, and boron.

soap    →   sapun

Soap is a salt of a fatty acid. For example, sodium stearate is a soap made by neutralizing stearic acid. Commercial soaps are mixtures of fatty acid salts.

supersaturated solution    →   prezasićena otopina

Solution is supersaturated when it contains greater quantity of dissolved substance in itself than it corresponds to solubility of that substance at that temperature. It is said to be in an unstable state, and by shaking the vessel containing that such a solution separation of salt surplus can occur.

tempering    →   kaljenje

Tempering is a rapid cooling of metals (often steels) from a suitable elevated temperature, thus changing its properties, e.g. steel becomes harder. This is generally accomplished by immersion in water, oil, polymer solution, or salt, although forced air is sometimes used.