CHEMISTRY GLOSSARY

pickling    →   dekapiranje

Pickling is a process to chemically remove scale or oxide from steel to obtain a clean surface. When applied to bars or coils prior to bright drawing, the steel is immersed in a bath of dilute sulphuric acid (w(H₂SO₄) = 10 %) heated to a temperature of around 80 °C. An inhibitor is added to prevent attack and pitting of the cleaned metal. After pickling, a washing process takes place followed by immersion in a lime-water bath to neutralise any remaining acid.

platinum    →   platina

Platinum was discovered by Antonio de Ulloa (South America) in 1735. The origin of the name comes from the Spanish word platina meaning silver. It is rare, very heavy, soft, silvery-white metal. Resists oxygen and water. Platinum is produced from deposits of native, or elemental. Used in jewellery, to make crucible and special containers and as a catalyst. Used with cobalt to produce very strong magnets. Also to make standard weights and measures. Resists corrosion and acid attacks except aqua regia.

plutonium    →   plutonij

Plutonium was discovered by Glenn T. Seaborg, Edwin M. McMillan, J. W. Kennedy and A. C. Wahl (USA) in 1940. Named after the planet Pluto. It is silvery-white, extremely radioactive artificially produced metal. Reacts with oxygen and acids; resists alkalis. Attacked by steam. Highly toxic. Plutonium is found rarely in some uranium ores. Made by bombarding uranium with neutrons. Used in bombs and reactors. Small quantities are used in thermo-electric generators.

polonium    →   polonij

Polonium was discovered by Marie Curie (Poland) in 1898. Named for Poland, native country of Marie Curie. It is silvery-grey, extremely rare, radioactive metal. Soluble in dilute acids. Highly toxic. Severe radiotoxicity. Carcinogen. Polonium occurs in pitchblende. Produced by bombarding bismuth with neutrons. Used in industrial equipment that eliminates static electricity caused by such processes as rolling paper, wire and sheet metal.

polyester    →   poliester

Polyesters are copolymers formed by condensation polymerization of dicarboxylic acid (terephthalic acid) and a dialcohol, also called a diol (ethylene glycol).

praseodymium    →   praseodimij

Praseodymium was discovered by Carl F. Auer von Welsbach (Austria) in 1885. The origin of the name comes from the Greek words prasios didymos meaning green twin. It is silvery white, moderately soft, malleable, ductile metal. Reacts slowly with oxygen. Reacts rapidly with water. Metal ignites and burns readily. Praseodymium is obtained from same salts as neodymium. Used with neodymium to make lenses for glass maker’s goggles since it filters out the yellow light present in glass blowing. Alloyed with magnesium creates a high-strength metal used in aircraft engines. Misch metal, used in the manufacture of pyrophoric alloys for cigarette lighters, contains about 5 % praseodymium metal. (Typically composition of misch metal are Ce:Nd:Pr:La:Other rare earth=50:18:6:22:4).

proline    →   prolin

Proline has an aliphatic side chain with a distinctive cyclic structure. It is unusual because it is conformationally restricted. The secondary amino (imino) group of proline residues is held in a rigid conformation that reduces the structural flexibility of polypeptide regions containing proline. It is not an essential amino acid, which means that the human body can synthesize it.

• Abbreviations: Pro, P
• IUPAC name: pyrrolidine-2-carboxylic acid
• Molecular formula: C₅H₉NO₂
• Molecular weight: 115.13 g/mol

protactinium    →   protaktinij

Protactinium was discovered by Otto Hahn (Germany) and Lise Meitner (Austria) in 1917. The origin of the name comes from the Greek word protos meaning first. It is very rare, silvery-white, extremely radioactive metal. Resists alkalis; reacts with oxygen and acids. Attacked by steam. Highly radiotoxic. Protactinium is extremely toxic and must be handled with great care. Protactinium does not occur in nature. Found among fission products of uranium, thorium and plutonium.

relative molecular mass    →   relativna molekularna masa

Relative molecular mass (M_r) is the ratio of the average mass per molecule or specified entity of a substance to 1/12 of the mass of nuclide ¹²C. Also called molecular weight. It is equal to the sum of the relative atomic masses of all the atoms that comprise a molecule. For example

M_r(H₂SO₄) = 2·A_r(H) + A_r(S) + 4·A_r(O)

= 2·1.0079 + 32.066 + 4·15.999

= 2.0158 + 32.066 + 63.996

= 98.078

rhenium    →   renij

Rhenium was discovered by Walter Noddack, Ida Tacke and Otto Berg (Germany) in 1925. The origin of the name comes from the Latin word Rhenus meaning river Rhine. It is rare and costly, dense, silvery-white metal. Tarnishes in moist air. Resists corrosion and oxidation. Dissolves in nitric and sulfuric acids. Has a very high melting point. Rhenium is found in small amounts in gadolinite and molybdenite. Mixed with tungsten or platinum to make filaments for mass spectrographs. Its main value is as a trace alloying agent for hardening metal components that are subjected to continuous frictional forces.