CHEMISTRY GLOSSARY

solubility curve    →   krivulja topljivosti

Solubility curve is a graphic presentation of solubility change in dependence on temperature.

solubility    →   topljivost

Solubility is the maximum amount of solute that dissolves in a given quantity of solvent at a specific temperature. Generally, for a solid in a liquid, solubility increases with temperature; for a gas, solubility decreases. Common measures of solubility include the mass of solute per unit mass of solution (mass fraction), mole fraction of solute, molality, molarity, and others.

solubility product constant    →   konstanta produkta topljivosti

Solubility product constant (K_sp) (or the solubility product) is the product of the molar concentrations of the constituent ions, each raised to the power of its stoichiometric coefficient in the equilibrium equation. For instance, if a compound A_aB_b is in equilibrium with its solution

the solubility product is given by

aspartic acid    →   asparaginska kiselina

Aspartic acid is an electrically charged amino acids with acidic side chains. As a group the charged amino acids are relatively abundant and are generally located on the surface of the protein. Aspartic acid and glutamic acid play important roles as general acids in enzyme active centers, as well as in maintaining the solubility and ionic character of proteins. Aspartic acid (sometimes referred to as asparate depending on pH) is non-essential in mammals, being produced from oxaloacetate by transamination.

• Abbreviations: Asp, D
• IUPAC name: 2-aminobutanedioic acid
• Molecular formula: C₄H₇NO₄
• Molecular weight: 133.10 g/mol

chromatography    →   kromatografija

Chromatography is a method of separation of the components of a sample in which the components are distributed between two phases, one of which is stationary while the other moves. In gas chromatography, the gas moves over a liquid or solid stationary phase. In liquid chromatography, the liquid mixture moves through another liquid, a solid, or a gel. The mechanism of separation of components may be adsorption, differential solubility, ion-exchange, permeation, or other mechanisms.

electrode of the second kind    →   elektroda drugog reda

Electrodes of the second kind are metal electrodes assembly with the equilibrium potential being a function of the concentration of an anion in the solution. Typical examples are the silver/silver-chloride electrode and the calomel electrode. The potential of the metal is controlled by the concentration of its cation in the solution, but this, in turn, is controlled by the anion concentration in the solution through the solubility product of the slightly soluble metal salt. Contrast with electrode of the first kind and electrode of the third kind.

supersaturated solution    →   prezasićena otopina

Solution is supersaturated when it contains greater quantity of dissolved substance in itself than it corresponds to solubility of that substance at that temperature. It is said to be in an unstable state, and by shaking the vessel containing that such a solution separation of salt surplus can occur.

electrode of the third kind    →   elektroda trećeg reda

Electrode of the third kind is a metal electrode assembly with the equilibrium potential being a function of the concentration of a cation, other than the cation of the electrode metal, in the solution. The assembly consists of a metal in contact with two slightly soluble salts (one containing the cation of the solid metal, the other the cation to be determined, with both salts having a common anion) immersed in a solution containing a salt of the second metal (e.g., zinc metal--zinc oxalate--calcium oxalate--calcium salt solution). The potential of the metal is controlled by the concentration of its cation in the solution, but this is controlled by the anion concentration in the solution through the solubility product of the slightly soluble metal salt, which, in turn is controlled by the concentration of the cation of the second slightly soluble salt. These electrodes are very sluggish and unstable due to a series of equilibria to be established to produce a stable potential.

extraction    →   ekstrakcija

Extraction is the separation of a component from its mixture by selective solubility. When a solution of one substance in one solvent is brought in with another solvent dissolved substance will distribute between the two solutants because of different solubility. Extraction is an efficient and fast method used for separating and concentrating matters. Extraction is best done several times in a succession, with smaller amount of solvent in it the matter is better dissolved. For example, caffeine can be separated from coffee beans by washing the beans with supercritical fluid carbon dioxide; the caffeine dissolves in the carbon dioxide, but flavour compounds do not. Vanillin can be extracted from vanilla beans by shaking the beans with an organic solvent, like ethanol.

fatty acid    →   masna kiselina

Fatty acids are aliphatic monocarboxylic acids characterized by a terminal carboxyl group (R-COOH). The higher members of this series of acids occur in nature in the combined form of esters of glycerol (fats), and hence all acids of this family are called fatty acids. Natural fatty acids commonly have a chain of 4 to 28 carbons (usually unbranched and even-numbered), which may be saturated or unsaturated. The most important of saturated fatty acids are butyric (C4), lauric (C12), palmitic (C16), and stearic (C18). The most common unsaturated acids are oleic, linoleic, and linolenic (all C18).

The physical properties of fatty acids are determined by the chain length, degree of unsaturation, and chain branching. Short-chain acids are pungent liquids, soluble in water. As the chain length increases, melting points are raised and water-solubility decreases. Unsaturation and chain branching tend to lower melting points.