CHEMISTRY GLOSSARY

analytical balance    →   analitička vaga

Analytical balances are instruments used for precise determining mass of matter. Analytical balances are sensitive and expensive instruments, and upon their accuracy and precision the accuracy of analysis result depends. The most widely used type of analytical balances are balances with a capacity of 100 g and a sensitivity of 0.1 mg. Not one quantitative chemical analysis is possible without usage of balances, because, regardless of which analytical method is being used, there is always a need for weighing a sample for analysis and the necessary quantity of reagents for solution preparation.

The working part of the balance is enclosed in a glass-fitted case. The baseplate is usually of black glass or black slate. The beam has agate knife-edges at its extremes, supporting stirrups from which balance pans are suspended. Another agate or steel knife-edge is fixed exactly in the middle of the beam on its bottom side. This knife-edge faces downwards and supports the beam. When not in use and during loading or unloading of the pans, the balance should be arrested.

The principle of operation of a modern laboratory balance bears some resemblance to its predecessor - the equal arm balance. The older instrument opposed the torque exerted by an unknown mass on one side of a pivot to that of an adjustable known weight on the other side. When the pointer returned to the center position, the torques must be equal, and the weight was determined by the position of the moving weights.

Modern electronic laboratory balances work on the principle of magnetic force restoration. In this system, the force exerted by the object being weighed is lifted by an electromagnet. A detector measures the current required to oppose the downward motion of the weight in the magnetic field.

carat    →   karat

Carat (ct.) is a metric unit of mass for the weighing of precious metals, precious stone and gems (e.g. diamond, ruby, sapphire).

Carat (ct, Kt) corresponds to the mass fraction of gold in precious alloys used in jewellery.

1 ct = 0.4167 %

24 ct = 100 %

24 carat gold is pure gold, 18 carat is 75 % gold and 25 % of some other metal such as silver or copper.

cement    →   cement

Cement is any various substances used for bonding or setting to a hard material. Portland cement is a mixture of calcium silicates and aluminates made by heating limestone (CaCO₃) with clay (containing aluminosilicates) in a kiln. The product is ground to a fine powder. When mixed with water it settles in a few hours and then hardens over a longer period of time due to the formation of hydrated aluminates and silicates.

chlorine    →   klor

Chlorine was discovered by Carl William Scheele (Sweden) in 1774. The origin of the name comes from the Greek word chloros meaning pale green. It is greenish-yellow, disagreeable gas with irritating odour. Gas is toxic and severe irritant by contact or inhalation. Never found in free form in nature. Commercial quantities of chlorine are produced by electrolysis of aqueous sodium chloride (NaCl) from seawater or brine from salt mines. Used in water purification, bleaches, acids and many, many other compounds such as chlorofluorocarbons (CFC).

coke    →   koks

Coke is a hard, dry carbon substance produced by heating coal to a very high temperature in the absence of air. It is used in the manufacture of iron and steel.

diamond    →   dijamant

Diamond is the hardest known mineral (with a hardness of 10 on Mohs’ scale). It is an allotropic form of pure carbon that has crystallised in the cubic system, usually as octahedral or cubes, under great pressure. Diamond crystals my be colourless and transparent or yellow, brown or black. They are highly prized as gemstones, but also have extensive uses in industry, mainly for cutting and grinding tools. Diamonds occur in ancient volcanic pipes of kimberlite, or in river deposits that have been derived from weathered kimberlite. Industrial diamonds are being increasingly synthetically produced.

dolomite    →   dolomit

Dolomite is a carbonate mineral consisting of a mixed calcium-magnesium carbonate, CaCO₃·MgCO₃, crystallising in the rhombohedral system. It is usually white or colourless. The term is also used to denote a rock with a high ratio of magnesium to calcium carbonate.

explosive    →   eksploziv

Explosive is a compound or mixture that, when ignited or detonated, undergoes rapid violent chemical reaction that produces large amount of gas and heat, accompanied by light, sound and a high pressure shock wave.

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

gunpowder    →   barut

Gunpowder (black powder) is a low explosive composed of potassium nitrate, sulphur and charcoal. Typical proportions are 6:1:1.