CHEMISTRY GLOSSARY

titar    →   titar

Titar (T) is a mass of titrated matter which is equivalent to 1 cm³ of solution. It is shown as T = 2.356 mg HCl / 1.0 cm³ NaOH, 0.1000 moldm^-3, and it is usually shown in a table form. If the concentration of used standard solution (c) differs from one outlined in the table data (c₀), the factor of correction (f) is induced

Titar is usually used in industrial operational laboratories where from titar tables mass or percentage of the ingredient in question is directly read.

toxin    →   toksin

Toxins are effective and specific poisons produced by living organisms. They usually consist of an amino acid chain which can vary in molecular weight between a couple of hundred (peptides) and one hundred thousand (proteins). They may also be low-molecular organic compounds. Toxins are produced by numerous organisms, e.g., bacteria, fungi, algae and plants. Many of them are extremely poisonous, with a toxicity that is several orders of magnitude greater than the nerve agents. Botulinum toxin, produced by the bacteria Clostridium botulinum, is the most poisonous substance known.

triple point    →   trojna točka

Triple point is the point in p,T space where the solid, liquid, and gas phases of a substance are in thermodynamic equilibrium.

tyrosine    →   tirozin

Tyrosine is hydrophobic amino acids with aromatic side chain. Tyrosine is large aromatic residue that is normally found buried in the interior of a protein and is important for protein stability. Tyrosine has special properties since its hydroxyl side chain may function as a powerful nucleophile in an enzyme active site (when ionized) and is a common site for phosphorylation in cell signaling cascades. Tyrosine absorbs ultraviolet radiation and contributes to the absorbance spectra of proteins. It is not essential (or semi-essential) to the human diet, since it is synthesized in the body from other metabolites.

• Abbreviations: Tyr, Y
• IUPAC name: 2-amino-3-(4-hydroxyphenyl)propanoic acid
• Molecular formula: C₉H₁₁NO₃
• Molecular weight: 181.19 g/mol

valence electron    →   valentni elektron

Valence electrons are electrons that can be actively involved in a chemical change, usually electrons in the outermost (valent) shell. For example, sodium’s ground state electron configuration is 1s² 2s² 2p⁶ 3s¹; the 3s electron is the only valence electron in the atom. Germanium (Ge) has the ground state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p²; the 4s and 4p electrons are the valence electrons.

van der Waals’ equation    →   van der Waalsova jednadžba

Van der Waals’ equation is an equation of state for real fluids which takes the form:

where p is pressure, V_m is molar volume, T is temperature, R is the molar gas constant, and a and b are characteristic parameters of the substance which describe the effect of attractive and repulsive intermolecular forces.

volume concentration    →   volumenska koncentracija

Volume concentration (σ) is equal to volume (V_A) of solute and volume (V) of solution proportion. Volume concentration differs from volume fraction because the sum of solution components volume is almost always different than the solution volume.

volume fraction    →   volumenski udio

Volume fraction (φ_A) is defined as

where V_A is the volume of the specified component and the V_i are the volumes of all the components of a mixture prior to mixing.

Winkler’s method    →   Winklerova metoda

Winkler’s method was once a common method used to determine the dissolved oxygen concentration by titration. Now rarely used due to the accuracy and low price of oxygen meters.

The water sample is first treated with excess manganese(II) sulfate solution and then with an alkaline solution of potassium iodide. The Mn(OH)₂ initially formed reacts with the dissolved oxygen. The amount of MnO(OH)₂ formed is determined by reaction with iodide ion in acidic solution. The iodine formed may be titrated against standard thiosulfate solution, using starch as an indicator.

Wohler’s synthesis    →   Wohlerova sinteza

Wöhler’s synthesis is a synthesis of urea performed by the German chemist Friedrich Wöhler (1800-1882) in 1828. He discovered that urea (CO(NH₂)₂) was formed when a solution of ammonium isocyanate (NH₄NCO) was evaporated. At the time it was believed that organic substances such as urea could only be made by living organisms, and its production from an inorganic compound was a notable discovery.