CHEMISTRY GLOSSARY

hassium    →   hassij

Hassium was discovered by Peter Armbruster, Gottfried Münzenber and their co-workers at the Heavy Ion Research Laboratory (Gesellschaft für Schwerionenforschung, GSI) in Darmstadt, Germany in 1984. The origin of the name is the Latin word Hassias meaning Hess, the German state. It is synthetic radioactive metal. Hassium was produced bythe bombardment of lead-208 with iron-58.

histidine    →   histidin

Histidine is an electrically charged amino acids with basic side chains. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested. Histidine is perhaps the most common and versatile catalytic residue in proteins. The imidazole sidechain of histidine has a pKa of approximately 6.0. This means that, at physiologically relevant pH values, relatively small shifts in pH will change its average charge. The unprotonated imidazole is nucleophilic and can serve as a general base, while the protonated form can serve as a general acid. In addition, it is often a ligand for transition metal ions such as iron and zinc.

• Abbreviations: His, H
• IUPAC name: 2-amino-3-(1H-imidazol-5-yl)propanoic acid
• Molecular formula: C₆H₉N₃O₂
• Molecular weight: 155.15 g/mol

indium    →   indij

Indium was discovered by Ferdinand Reich and Hieronymus Theodor Richter (Germany) in 1863. Named after the indicum (colour indigo), the colour it shows in a spectroscope. It is rare, very soft, silver-white metal. Stable in air and water. Dissolves in acids. Metal can ignite and burn. Indium is found in certain zinc ores. Used to coat high speed bearings and as an alloy that lowers the melting point of other metals. Relatively small amounts are used in dental items and in electronic semiconductors.

manganese    →   mangan

Manganese was discovered by Johann Gahn (Sweden) in 1774. The origin of the name comes from the Latin word magnes meaning magnet, or magnesia nigri meaning black magnesia (MnO₂). It is hard, brittle, grey-white metal with a pinkish tinge. Impure forms are reactive. Rusts like iron in moist air. Manganese is most abundant ores are pyrolusite (MnO₂), psilomelane [(Ba,H₂O)₂Mn₅O₁₀] and rhodochrosite (MnCO₃). Pure metal produced by mixing MnO₂ with powered Al and ignited in a furnace. Used in steel, batteries and ceramics. The steel in railroad tracks can contain as much as 1.2 % manganese. It is crucial to the effectiveness of vitamin B₁.

nickel    →   nikal

Nickel was discovered by Axel Fredrik Cronstedt (Sweden) in 1751. The origin of the name comes from the German word kupfernickel meaning Devil’s copper or St Nicholas’s (Old Nick’s) copper. It is hard, malleable, silvery-white metal. Soluble in acids, resist alkalis. It can be polished to a lustrous finish. Resists corrosion in air under normal conditions. Nickel is chiefly found in pentlandite [(Ni,Fe)₉S₈] ore. The metal is produced by heating the ore in a blast furnace which replaces the sulfur with oxygen. The oxides are then treated with an acid that reacts with the iron not the nickel. Used in electroplating and metal alloys because of its resistance to corrosion. Also in nickel-cadmium batteries, as a catalyst and for coins.

polymorphism    →   polimorfija

Polymorphism is the ability of a solid substance to crystallise into more than one different crystal structure. Different polymorphs have different arrangements of atoms within the unit cell, and this can have a profound effect on the properties of the final crystallised compound. The change that takes place between crystal structures of the same chemical compound is called polymorphic transformation.

The set of unique crystal structures a given compound may form are called polymorphs. Calcium carbonate is dimorphous (two forms), crystallizing as calcite or aragonite. Titanium dioxide is trimorphous; its three forms are brookite, anatase, and rutile. The prevailing crystal structure depends on both the temperature and the external pressure.

Iron is a metal with polymorphism structure. Each structure stable in the range of temperature, for example, when iron crystallizes at 1 538 °C it is bcc (δ-iron), at 1 394 °C the structure changes to fcc (γ-iron or austenite), and at 912 °C it again becomes bcc (α-iron or ferrite).

Polymorphism of an element is called allotropy.

redox titration    →   redoks-titracija

Redox titration (oxidation-reduction titration) is a titration based on a redox reaction. For example, iron in water can be determined by converting dissolved iron to Fe²⁺ and titrating the solution with potassium permanganate (KMnO₄), a powerful oxidising agent.

reducing agent    →   redukcijsko sredstvo

Reducing agent may be defined in various ways, depending upon the context in which the phrase is used. In broad terms it is often taken to mean a chemical which can act as an electron donor. Thus, in the reaction:

the zinc is being reduced (gaining electrons) by reaction with the iron cations; the Fe²⁺ in this instance is acting as a reducing agent.

sacrificial protection    →   zaštita žrtvovanom elektrodom

Sacrificial protection is the protection of iron or steel against corrosion by using a more reactive metal. Pieces of zinc or magnesium alloy are attached to pump bodies and pipes. The protected metal becomes the cathode and does not corrode. The anode corrodes, thereby providing the desired sacrificial protection. These items are known as sacrificial anodes and "attract" the corrosion to them rather than the iron/steel. The sacrificial anodes must be replaced periodically as they corrode.

The iron pipe will be connected to a more reactive metal such as magnesium through cooper wires, the magnesium will donate its electrons to the iron preventing it from rusting. Iron which is oxidises will immediately be reduced back to iron.

thallium    →   talij

Thallium was discovered by Sir William Crookes (England) in 1861. The origin of the name comes from the Greek word thallos meaning green twig or green shoot. It is soft grey metal that looks like lead. Tarnishes in moist air. Reacts in heated moist air and in acids. Compounds highly toxic by inhalation or ingestion. Cumulative effects. Thallium is found in iron pyrites. Also in crookesite, hutchinsonite and lorandite. Most is recovered from the by-products of lead and zinc refining. Its compounds are used in rat and ant poisons. Also for detecting infrared radiation.