CHEMISTRY GLOSSARY

Graham’s law    →   Grahamov zakon

Graham’s law is the rates at whish gases diffuse are inversely proportional to the square roots of their densities. This principle is made use of in the diffusion method of separating isotopes. The law was formulated in 1829 by British chemist Thomas Graham (1805-1869).

Ilkovic equation    →   Ilkovičeva jednadžba

Ilkovic equation is a relation used in polarography relating the diffusion current (i_d) and the concentration of the depolarizer (c), which is the substance reduced or oxidized at the dropping mercury electrode. The Ilkovic equation has the form

Where k is a constant which includes Faraday constant, π and the density of mercury, and has been evaluated at 708 for max current and 607 for average current, D is the diffusion coefficient of the depolarizer in the medium (cm²/s), n is the number of electrons exchanged in the electrode reaction, m is the mass flow rate of Hg through the capillary (mg/sec), and t is the drop lifetime in seconds, and c is depolarizer concentration in mol/cm³.

The equation is named after the scientist who derived it, the Slovak chemist, Dionýz Ilkovič 1907-1980).

lutetium    →   lutecij

Lutetium was discovered by Georges Urbain (France) and independently by Carl Auer von Welsbach (Austria) in 1907. The origin of the name comes from the Greek word Lutetia meaning Paris. It is silvery-white and relatively stable in air, rare earth metal. Lutetium is found with ytterbium in gadolinite and xenotime. Stable lutetium nuclides can be used as catalysts in cracking, alkylation, hydrogenation, and polymerization.

Knudsen burette    →   Knudsenova bireta

Knudsen's automatic bulb-burette, developed by the Danish physicist Martin Knudsen (1871-1949), is designed in a way that even routine field analysis in a boat laboratory would provide highly accurate measurements. The burette is filled with a mixture of silver nitrate from reservoir R, located above the burette, by opening the A valve. When the solution crosses the three-way C valve the A valve is closed preventing further solution flow in to the burette. Any extra solution is caught in the W bowl. Turn the C valve, which marks the zero on the scale, in order to allow atmospheric air to enter the burette. Since most open-ocean samples lie in a relatively small chlorinity range, the burette is designed so that much of its capacity is in the bulb (B). This allows the titration to be quick (by quickly releasing contents from the B area) and reduces the error that occurs from the slow drainage along the inner wall of the burette.

Each millimeter is divided in to twenty parts (double millimeter division of the Knudsen burette) which allows for highly accurate measurements (the scale is read up to a precision of 0.005 mL). From 0 to 16 the burette isn't divided, that usually starts from 16 and goes until 20.5 or 21.5. A single double millimeter on a Knudsen burette scale corresponds to one permille of chloride in the seawater sample. This burette can be used for titration of water from all of the oceans and seas, with the exemptions being areas with very low salinity (e.g. the Baltic Sea) and river estuaries which require the use of normal burettes.

macromolecule    →   makromolekule

Macromolecule is a molecule of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetitions of units derived, actually or conceptually, from molecules of low relative molecular mass. The types of macromolecules are natural and synthetic polymers, carbohydrates, lipids, proteins etc. Cellulose is a polysaccharide that is made up of hundreds, even thousands of glucose molecules strung together.

lead-acid battery    →   olovni akumulator

Lead-acid battery is a electrical storage device that uses a reversible chemical reaction to store energy. It was invented in 1859 by French physicist Gaston Planté. Lead-acid batteries are composed of a lead(IV) oxide cathode, a sponge metallic lead anode and a sulphuric acid solution electrolyte.

In charging, the electrical energy supplied to the battery is changed to chemical energy and stored. The chemical reaction during recharge is normally written:

In discharging, the chemical energy stored in the battery is changed to electrical energy. During discharge, lead sulfate (PbSO4) is formed on both the positive and negative plates. The chemical reaction during discharge is normally written:

Lead acid batteries are low cost, robust, tolerant to abuse, tried and tested. For higher power applications with intermittent loads however, they are generally too big and heavy and they suffer from a shorter cycle life.

magnetic permeability    →   magnetska permeabilnost

Magnetic permeability (μ), also called permeability, is a constant of proportionality that exists between magnetic induction and magnetic field intensity. This constant is equal to approximately μ_o = 1.257×10^-6 H/m in a vacuum.

Magnetic permeability is often expressed in relative, rather than in absolute, terms. If μ represents the permeability of the substance in question, then the relative permeability, μ_r, is given by:

mass-energy equivalence    →   ekvivalencija mase i energije

In the special theory of relativity Einstein demonstrated that neither mass nor energy were conserved separately, but that they could be traded one for the other and only the total "mass-energy" was conserved. The relationship between the mass and the energy is contained in what is probably the most famous equation in science,

Where m is the mass of the object and c is the velocity of light. Cockcroft and Walton (1932) are routinely credited with the first experimental verification of mass-energy equivalence.

molar mass    →   molarna masa

Molar mass is the mass of one mole of a substance.

It is normally expressed in units of g mol^-1, in which case its numerical value is identical with the relative molecular mass.

nuclear magnetic resonance    →   nuklearna magnetska rezonancija

Nuclear magnetic resonance (NMR) is a type of radio-frequency spectroscopy based on the magnetic field generated by the spinning of electrically charged atomic nuclei. This nuclear magnetic field is caused to interact with a very large (1 T - 5 T) magnetic field of the instrument magnet. NMR techniques have been applied to studies of electron densities and chemical bonding and have become a fundamental research tool for structure determinations in organic chemistry.