CHEMISTRY GLOSSARY

Zimmermann-Reinhardt’s reagent    →   Zimmermann-Reinhardtov reagens

Zimmermann-Reinhardt’s reagent is a mixture of manganese(II) sulphate, sulphuric acid and phosphorus acid. It is used for preventing oxidation of chloride ion while titrating iron(II) ion with permanganate solution.

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.

Kohlrausch’s law    →   Kohlrauschov zakon

Kohlrausch’s law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations. If a salt is dissolved in water, the conductivity of the solution is the sum of the conductances of the anions and cations. The law, which depends on the independent migration of ions, was deduced experimentally by the German chemist Friedrich Kohlrausch (1840-1910).

law of conservation of mass    →   zakon o očuvanju mase

Law of conservation of mass states that no detectable gain or loss in mass occurs in chemical reactions. The state of a substance may change in a chemical reaction, for example, from a solid to a gas, but its total mass will not change. Note that the energy released (exothermic) or adsorbed (endothermic) in a chemical reaction is a result of energy transfer between atoms and their environment.

lithosphere    →   litosfera

Lithosphere (from the Greek for rocky sphere) is rigid, rocky outer layer of the Earth, consisting of the crust and the solid outermost layer of the upper mantle. The distinguishing characteristic of the lithosphere is not its composition but its flow properties. It floats on the asthenosphere, which is the heat-softened layer of the mantle below the lithosphere.

The lithospheric is not one continuous piece but is broken into about a dozen major separate rigid blocks, or plates, which move independently relative to one another. This movement of lithospheric plates over the asthenosphere is described as plate tectonics. When an oceanic plate and a continental plate meet, the heavier oceanic plate (composed mostly of basalt, specific gravity about 3.0 or peridotite, specific gravity about 3.3) subducts under the lighter continental plate (composed mostly of granite, specific gravity about 2.7).

low-density polyethylene    →   polietilen niske gustoće

Low-density polyethylene (LDPE) is a thermoplastic polyolefin with a density of 0.910-0.940 g cm^-3. It is a recyclable plastic used predominantly in film applications due to its toughness, flexibility and relative transparency. LDPE has a low melting point, making it popular for use in applications where heat sealing is necessary. Typically, LDPE is used to manufacture flexible films such as those used for plastic retail bags and garment dry cleaning and grocery bags.

mass concentration    →   masena koncentracija

Mass concentration (γ) is equal to mass (m_A) of soluted substance and volume (V) of the solution proportion. SI unit for mass concentration is kg m^-3, but in laboratory practice g dm^-3, which has the same number value, is often used.

mass fraction    →   maseni udio

Mass fraction (w_A) is the ratio of the mass of substance A to the total mass of a mixture.

measuring cylinder    →   menzura

Measuring cylinders (graduated cylinders) are graduated glass cylinders with a capacity from 2 mL to 2 L. They are used when reagent solutions for volume measuring are prepared when accuracy is not of great relevance. The larger the measuring cylinder, the bigger the measuring error.

melting point    →   talište

Melting point is the temperature at which a solid becomes a liquid at normal atmospheric pressure.

A more specific definition of melting point (or freezing point) is the temperature at which the solid and liquid phases of a substance are in equilibrium at a specified pressure (normally taken to be atmospheric unless stated otherwise). A pure substance under standard condition of pressure has a single reproducible melting point. The terms melting point and freezing point are often used interchangeably, depending on whether the substance is being heated or cooled.