CHEMISTRY GLOSSARY

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.

latex    →   lateks

Latex, also known as rubber or natural latex, is a milky fluid derived from the rubber tree. The latex is a colloid of caoutchouc (25-35%) dispersed in water (60-75%), which forms rubber by coagulation. The term is also applied to artificial emulsions of natural or artificial rubber, or of certain synthetic resins (such as polyvinyl acetate or polyvinyl chloride). It is used in a wide variety of consumer products, including rubber gloves, tubing, condoms, rubber bands, etc.

lithium    →   litij

Lithium was discovered by Johan August Arfvedson (Sweden) in 1817. The origin of the name comes from the Greek word lithos meaning stone, apparently because it was discovered from a mineral source whereas the other two elements, sodium and potassium, were discovered from plant sources. It is soft silvery-white metal. Lightest of metals. Reacts slowly with water and oxygen. Flammable. Can ignite in air. Reacts with water to give off a flammable gas. Lithium is obtained by passing electric charge through melted lithium chloride and from the silicate mineral called spodumene [LiAl(Si₂O₆)]. Used in batteries. Also for certain kinds of glass and ceramics. Some is used in lubricants.

magnesium    →   magnezij

Magnesium was discovered by Sir Humphry Davy (England) in 1808. The origin of the name comes from the Greek word Magnesia, a district of Thessaly. It is lightweight, malleable, silvery-white metal. Burns in air with a brilliant white flame and reacts with water as temperature elevates. Can ignite in air. React violently with oxidants. Magnesium is found in large deposits in the form of magnesite, dolomite and other minerals. It is usually obtained by electrolysis of melted magnesium chloride (MgCl₂) derived from brines, wells and sea water. Used in alloys to make airplanes, missiles and other uses for light metals. Have structural properties similar to aluminium.

mineral    →   mineral

Minerals are compounds in which metals can be found in nature. Metals in nature can appear as:

mustard agent    →   plikavac

Mustard agents are usually classified as blistering agents owing to the similarity of the wounds caused by these substances resembling burns and blisters. However, since mustard agents also cause severe damage to the eyes, respiratory system and internal organs, they should preferably be described as blistering and tissue-injuring agents. Normal mustard agent (yperite), 1,1-thio-bis-[2-chloroethane], reacts with a large number of biological molecules. The effect of mustard agent is delayed and the first symptoms do not occur between 2-24 hours after exposure. At room temperature, mustard agent is a liquid with low volatility and is very stable during storage.

osmium    →   osmij

Osmium was discovered by Smithson Tennant (England) in 1803. The origin of the name comes from the Greek word osme meaning smell. It is hard fine black powder or hard, lustrous, blue-white metal. Unaffected by air, water and acids. Characteristic acrid, chlorine like odour due to tetroxide compound. Osmium tetroxide highly toxic. Osmium is obtained from the same ores as platinum. Used to tip gold pen points, instrument pivots, to make electric light filaments. Used for high temperature alloys and pressure bearings. Very hard and resists corrosion better than any other.

polymerization    →   polimerizacija

Polymerization is a reaction of connecting many monomers in one long molecule whereby polymers are created.

potassium    →   kalij

Potassium was discovered by Sir Humphry Davy (England) in 1807. The origin of the name comes from the Arabic word qali meaning alkali (the origin of the symbol K comes from the Latin word kalium). It is soft, waxy, silver-white metal. Fresh surface has silvery sheen. Quickly forms dull oxide coating on exposure to air. Reacts strongly with water. Reacts with water to give off flammable gas. Reacts violently with oxidants. Occurs only in compounds. Potassium is found in minerals like carnallite [(KMgCl₃)·6H₂O] and sylvite (KCL). Pure metal is produced by the reaction of hot potassium chloride and sodium vapours in a special retort. Used as potash in making glass and soap. Also as saltpetre, potassium nitrate (KNO₃) to make explosives and to colour fireworks in mauve. Vital to function of nerve and muscle tissues.

practical salinity    →   praktični salinitet

Practical salinity S_P is defined on the Practical Salinity Scale of 1978 (PSS-78) in terms of the conductivity ratio K₁₅ which is the electrical conductivity of the sample at temperature t₆₈ = 15 °C and pressure equal to one standard atmosphere, divided by the conductivity of a standard potassium chloride (KCl) solution at the same temperature and pressure. The mass fraction of KCl in the standard solution is 0.0324356 (32.4356 g of KCl in 1 kg of solution). When K₁₅ = 1, the Practical Salinity P S is by definition 35. The conductivity of that reference solution is C(35,1568,0) = 42.914 mS/cm = 4.2914 S/m (Siemens per meter). Note that Practical Salinity is a unit-less quantity. Though sometimes convenient, it is technically incorrect to quote Practical Salinity in "psu". When K₁₅ is not unity, S_P and K₁₅ are related by the PSS-78 equation

At a temperature of t₆₈ = 15 °C, R_t is simply K₁₅ and Practical Salinity S_P can be determined from the above equation. For temperatures other than t₆₈ = 15 °C, Practical Salinity S_P is given by the following function of R_t (k = 0.0162)