CHEMISTRY GLOSSARY

ampere    →   amper

Ampere (A) is the SI base unit of electric current.

The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2×10^-7 newton per metre of length.

electrodialysis    →   elektrodijaliza

Electrodialysis is a procedure of dialysis accelerated with an electric field. Dialyser is divided into three sections. Solution flows through the middle section, between two semipermeable membranes alternately to positive ions and negative ions. An electrodes are placed in the neighbouring sections. Under the influence of electric field, positive ions will travel towards the cathode (the negative electrode), and negative ions towards the anode (the positive electrode), whereby travelling of ions through the membrane is accelerated. In this way, the feed water is separated into two streams: one of pure water and the other of more concentrated solution.

hypsometric curve    →   hipsometrijska krivulja

Hypsometric curve (or hypsographic curve) shows the distribution of height of a given area (on land) and depth (at sea). The term originates from the Greek word hypsos meaning height. The part of the curve that reflects the cross section of the ocean bottom is called the bathygraphic curve.

Horizontal dashed lines indicate average height of the continents at 840 meters above sea level, and average depth of the oceans at 3 682.2 meters below sea level. If all the land above sea level (green) was moved into the sea (blue), the oceans would still be 3 km deep.

nuclear reactor    →   nuklearni reaktor

Nuclear reactor is an assembly of fissionable material (uranium-235 or plutonium-239) designed to produce a sustained and controllable chain reaction for the generation of electric power.

The essential components of a nuclear reactor are:

1. The core, metal rods containing enough fissionable material to maintain a chain reaction at the necessary power level (as much as 50 t of uranium may be required).
2. A source of neutrons to initiate the reaction (such as a mixture of polonium and beryllium)
3. A moderator to reduce the energy of fast neutrons for more efficient fission (material such as graphite, beryllium, heavy water, and light water are used)
4. A coolant to remove the fission-generated heat (water, sodium, helium, and nitrogen may be used)
5. A control system such as rods of boron or cadmium that have high capture cross sections (to absorb neutrons)
6. Adequate shielding, remote-control equipment, and appropriate instrumentation are essential for personnel safety and efficient operation.

resistance    →   električni otpor

Electrical resistance (R) of a given object is the opposition to the passage of an electric current through that object. The SI unit of electrical resistance is the ohm, represented by the Greek letter omega (Ω). Resistance is the electric potential difference divided by the current when there is no electromotive force in the conductor. This definition applies to direct current. For a conductor of uniform cross section with area A and length L, and whose resistivity is ρ, the resistance is given by

resistivity    →   električna otpornost

Electrical resistivity, or specific resistance (ρ) is the electric field strength divided by the current density when there is no electromotive force in the conductor. Resistivity is an intrinsic property of a material. Materials with low resistivity are good conductors of electricity and materials with high resistivity are good insulators.

For a conductor of uniform cross section with area A and length L, and whose resistance is R, the resistivity is given by

The SI unit is Ω m.

water jet vacuum pump    →   vodena sisaljka

The water jet vacuum pump or vacuum aspirator is one of the most popular devices that produces vacuum in laboratories. The rapid flow of water through the device creates a vacuum in a side-arm that is connected to a vacuum application such a Buchner flask. The water jet vacuum pump creates a vacuum by means of Venturi effect named after the Italian physicist Giovanni Battista Venturi (1746–1822). The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. Water jet pumps are manufactured of glass, plastic or metal, depending on the conditions in which they are used.