CHEMISTRY GLOSSARY

parallax    →   paralaksa

Parallax is a deceptive change of the position of an object which is observed while the position of the observer changes. Position of eye at all volumetric vessels must be at the same level as the meniscus. If not, the parallax will cause an error while reading the position of the meniscus of a liquid in a burette. It will be a positive mistake if the eye is lower, and negative if the eye is higher than the meniscus plane.

Paschen series    →   Paschenova serija

Paschen series are the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the state with principal quantum number n = 3 and successive higher states.

peptide    →   peptid

Peptides are amides derived from two or more amino acids (the same or different) linked by peptide bonds. These bonds are formed by the reaction between adjacent carboxyl (-COOH) and amino (-NH₂) groups with the elimination of water.

peptide bond    →   peptidna veza

Peptide bond emerges when two amino acid join in a way that the carbon atom from one connects with the nitrogen atom from the other (creating a C-N bond).

period    →   perioda

Periods are horizontal rows in the periodic table, each period begin with an alkali metal (one electron in the outermost principal quantum level) and ending with a noble gas (each having eight electrons in the outermost principal quantum level, except for helium, which is limited to two).

periodic table of the elements    →   periodni sustav elemenata

Periodic table is a table of elements, written in sequence in the order of atomic number or atomic weight and arranged in horizontal rows (periods) and vertical columns (groups) to illustrate the occurrence of similarities in the properties of the elements as a periodic function of the sequence. The original form was proposed by Dmitri Mendeleev (1834-1907) in 1869, using relative atomic masses.

Petri dish    →   Petrijeva zdjelica

Petri dish is a shallow glass or plastic flat bottomed dish with a lid. Used primarily in laboratories for the culture of bacteria and other microorganisms on specially prepared media. It was named after the German bacteriologist Julius Richard Petri (1852-1921) who invented it in 1877.

petroleum    →   nafta

Petroleum (crude oil) is a dark viscous liquid usually found under Earth’s surface or sea bottom. It is a very complex mixture of different compounds, mostly of hydrocarbonates of alkane, cycloalkane and aromatic sort whose composition is variable from oil field to oil field.

phase diagram    →   fazni dijagram

Phase diagram is a graphic representation of the equilibrium relationships between phases (such as vapour-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution.

The figure shows a typical phase diagram of an element or a simple compound. The stability of solid, liquid and gas phases depends on the temperature and the pressure. The three phases are in equilibrium at the triple point. The gas and liquid phases are separated by a phase transition only below the temperature of the critical point.

phenylalanine    →   fenilalanin

Phenylalanine is hydrophobic amino acids with aromatic side chain. It is quite hydrophobic and even the free amino acid is not very soluble in water. Phenylalanine is large aromatic residue that is normally found buried in the interior of a protein and is important for protein stability. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Phe, F
• IUPAC name: 2-amino-3-phenylpropanoic acid
• Molecular formula: C₉H₁₁NO₂
• Molecular weight: 165.19 g/mol