CHEMISTRY GLOSSARY

ether    →   eter

Ethers are organic compounds with a formula R-O-R, where R is not equal to H. They may be derived from alcohols by elimination of water, but the major method is catalytic hydration of olefins. They are volatile highly flammable compounds; when containing peroxides they can detonate on heating. The term ether is often used synonymously with diethyl ether.

fat    →   mast

Fats are esters of glycerol and long chain carboxylic acids. Fats occur widely in plants and animals as a means of storing food energy, having twice the calorific value of carbohydrates. Fats derived from plants and fish generally have a greater proportion of unsaturated fatty acids than those from mammals. Fats may be either solid or liquid at room temperature, depending on their structure and composition. Unsaturated fats are liquid at room temperature.

Plant oils may be hardened by the addition of hydrogen atoms, converting double bonds to single bonds. This process is known as hydrogenation. Hydrogenated vegetable oils are often present in margarine and other processed foods.

Alkali hydrolysis of fat with sodium hydroxide it gives glycerol and soap (i.e. a mixture of the sodium salts of the fatty acids).

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.

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.

van der Waals’ force    →   van der Waalsova sila

Van derWaals’ force is the weak attractive force between two molecules which arises from electric dipole interactions. It can lead to the formation of stable but weakly bound dimer molecules or clusters. They are named after the Dutch physicist Johannes van der Waals (1837-1923).

filter paper    →   filtar papir

Filter paper is a quantitative paper used for filtering and made of pure cellulose treated with hydrochloric and hydrofluoric acid. This kind of paper burns out practically without any remains (less than 0.0001 g ashes). Different types of paper are marked with numbers; qualitative bears marking 595 or 597 and quantitative 589 or 590. Dependable upon precipitate character, different types of filter paper are used:

• black band (589¹) - 100 mL of fluid flows through it in 20 s to 30 s. It is used for filtering of gelatinous precipitates.
• white band (589²) - 100 mL of fluid flows through it in 40 s to 60 s. It is used for coarse crystalline precipitates filtration.
• blue band (589³) - 100 mL of fluid flows through it in 200 s to 400 s. It is used for fine crystalline precipitates.

wax    →   vosak

Wax is an ester formed from long-chain fatty acids and alcohols that is usually solid at room temperature.

flammable limit    →   granica zapaljivosti

Flammable limits refer to the conditions under which a mixture of a flammable material and air may catch fire or explode. When vapour s of a flammable or combustible liquid are mixed with air in the proper proportions in the presence of a source of ignition, rapid combustion or an explosion can occur. The proper proportion is called the flammable range and is also often referred to as the explosive range. The flammable range includes all concentrations of flammable vapour or gas in air, in which a flash will occur or a flame will travel if the mixture is ignited.

The lower flammable limit (LEL) or the lower explosive limit is the lowest concentration of a flammable vapour or gas in air that will propagate a flame from an ignition source. The upper flammable limit (UEL) or the upper explosive limit is the highest concentration of a flammable vapour or gas in air that will propagate a flame from an ignition source. Any concentration between these limits can ignite or explode.

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.