CHEMISTRY GLOSSARY

atom    →   atom

Atom is an atom is the smallest particle of an element that retains the chemical properties of the element. Rutherford-Bohr’s model represents the atom as a positively charged core of a size around 10^-14 m composed of protons (positive particles) and neutrons (neutral particles) around which negatively charged electrons circle. The number of protons and electrons are equal, so the atom is an electrically a neutral particle. Diameter of the atom is about 10^-10 m.

atom radius    →   radijus atoma

Atoms and molecules have no strict boundaries. The volume of a free atom is usually defined as that volume that contains 90 % of electron cloud. The radius of an atom represents half of interatom distance of two identical atoms which are in touch but are not interconnected either by a covalent or an ionic bond, but with a very weak van der Waals’s bond.

automatic burette    →   automatska bireta

Automatic burette is used for series of tests. It is connected with a bottle which contains the titration solution. The air is pumped into the bottle by a small rubber air pump, created the pressure in the bottle which the rises the solution to the top of burette. When the the burette is full, the valve is released, the pressure in the bottle falls and the burette automatically sets itself to zero. Work with automatic burettes is by far faster and the consumption of standard solution is smaller.

bag filter    →   vrećasti filtar

Bag filter is a unit within a mechanical system that bellows in a bag form when air flows through, cleaning the air by collecting particles of foreign matter. This system of filtering is rated the most efficient- in a range of 92 % to 95 %. Vacuum cleaner have a cloth filter bag.

Bag filter system is an economical method of liquid filtration consisting of the pressure vessel, restrainer basket and micron rated filter bag. Liquid flow is from the inside to the outside of the bag - dirt is trapped inside the bag.

ball mill    →   kuglični mlin

Ball mill is a grinder for reducing hard materials to powder. The grinding is carried out by the pounding and rolling of a charge of steel or ceramic balls carried within the cylinder. The cylinder rotates at a relatively slow speed, allowing the balls to cascade through the mill base, thus grinding or dispersing the materials.

Type of ball mills, centrifugal and planetary mills, are devices used to rapidly grind materials to colloidal fineness (approximately 1 μm and below) by developing high grinding energy via centrifugal and/or planetary action.

balance    →   vaga

Balance is an instrument to measure the mass (or weight) of a body. Balance beam type scales are the oldest type and measure weight using a fulcrum or pivot and a lever with the unknown weight placed on one end of the lever, and a counterweight applied to the other end. When the lever is balanced, the unknown weight and the counterweight are equal. The equal-arm balance consists of two identical pans hung from either end of a centrally suspended beam. The unequal-arm balance is made with one arm of the balance much longer than the other.

More modern substitution balances use the substitution principle. In this calibrated weights are removed from the single lever arm to bring the single pan suspended from it into equilibrium with a fixed counter weight. The substitution balance is more accurate than the two-pan device and enables weighing to be carried out more rapidly.

Electromagnetic force restoration balances also use a lever system but a magnetic field is used to generate the force on the opposite end of the lever and balance out the unknown mass. The current used to drive the magnetic coil is proportional to the mass of the object placed on the platform.

Balmer series    →   Balmerova serija

Balmer series, Balmer lines is a series of lines in the emission spectrum of hydrogen that involve transitions to the n=2 state from states with n>2.

barometer    →   barometar

Barometer is an instrument that measures atmospheric pressure. A mercury barometer is a closed tube filled with mercury inverted in a mercury reservoir. The height of the mercury column indicates atmospheric pressure (with 1 atm = 760 mm of mercury). An aneroid barometer consists of an evacuated container with a flexible wall. When atmospheric pressure changes, the wall flexes and moves a pointer which indicates the changing pressure on a scale.

base-centered monoclinic lattice    →   bazno centrirana monoklinska rešetka

Base-centered or side-centered or end-centered monoclinic lattice (monoclinic-C), like all lattices, has lattice points at the eight corners of the unit cell plus additional points at the centers of two parallel sides of the unit cell. It has unit cell vectors a≠b≠c, and interaxial angles α=γ=90°≠β.

base-centered orthorhombic lattice    →   bazno centrirana ortorompska rešetka

Base-centered or side-centered or end-centered monoclinic lattice (orthorhombic-C), like all lattices, has lattice points at the eight corners of the unit cell plus additional points at the centers of two parallel sides of the unit cell. It has unit cell vectors a≠b≠c and interaxial angles α=β=γ=90°.