CHEMISTRY GLOSSARY

bag filter    →   vrećasti filtar

Bag filter is a unit within a mechanical system that bellows in a bag form when air flows through, cleaning the air by collecting particles of foreign matter. This system of filtering is rated the most efficient- in a range of 92 % to 95 %. Vacuum cleaner have a cloth filter bag.

Bag filter system is an economical method of liquid filtration consisting of the pressure vessel, restrainer basket and micron rated filter bag. Liquid flow is from the inside to the outside of the bag - dirt is trapped inside the bag.

Buchner funnel    →   Buchnerov lijevak

Büchner funnel is one device used for pressure assisted filtration. Buchner funnel is a cylindrical porcelain filtering funnel (glass and plastic funnels are also available) that has a perforated plate on which the flat filter paper is placed. A vacuum in the flask underneath the filter allows atmospheric pressure on the sample to force the liquid through the filter paper. It is named after the German chemist Ernst Wilhelm Büchner (1850-1925) who designed this funnel in 1885.

cellulose    →   celuloza

Cellulose, (C₆H₁₀O₅)_n, is a polysaccharide that consists of a long unbranched chain of glucose units linked by (1→4)-β-glycoside bonds. Nature uses cellulose primarily as a structural material to impart strength and rigidity to plants. Leaves, grasses, and cotton are primarily cellulose. The fibrous nature of extracted cellulose has led to its use in textile industry for the production of cotton, artificial silk, etc. Cellulose also serves as raw material for the manufacture of cellulose acetate, known commercially as acetate rayon, and cellulose nitrate, known as guncotton. Gunncotton is the major ingredient in smokeless powder, the explosive propellant used in artillery shells and in ammunition for firearms.

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.

clay triangle    →   trokut za žarenje

Clay triangle is a piece of laboratory equipment used in the process of heating substances by a Bunsen burner (e.g. to support a crucible when it’s being heated).

colloid    →   koloid

Colloids are systems in which there are two or more phases, with one (the dispersed phase) distributed in the other (the continuous phase). Moreover, at least one of the phases has small dimensions, in the range between 1 nm and 1 μm (10^-9 m – 10^-6 m). Dimension, rather than the nature of the material, is characteristic. In this size range, the surface area of the particle is large with respect to its volume so that unusual phenomena occur, e.g., the particles do not settle out of the suspension by gravity and are small enough to pass through filter membranes. Macromolecules (proteins and other high polymers) are at the lower limit of this range; the upper limit is usually taken to be the point at which the particles can be resolved in an optical microscope.

Colloidal particles may be gaseous, liquid, or solid, and occur in various types of suspensions:

Sols - dispersions of small solid particles in a liquid.

Emulsions - colloidal systems in which the dispersed and continuous phases are both liquids.

Gels - colloids in which both dispersed and continuous phases have a three-dimensional network throughout the material.

Aerosols - colloidal dispersions of liquid or solid particles in a gas.

Foams - dispersions of gases in liquids or solids.

haematite    →   hematit

Haematite is a mineral of iron(III) oxide Fe₂O₃. It is the most important ore of iron and usually occurs in two main forms: as a massive red kidney-shaped ore and as grey to black metallic crystals known as specular iron ore. Haematite is the major red colouring agent in rocks; the largest deposits are of sedimentary origin. In industry haematite is also used as a polishing agent (jeweller’s rouge) and in paints.

Hirsch funnel    →   Hirschov lijevak

Hirsch funnels are essentially smaller Büchner funnels and primarily used to collect a desired solid from a relatively small volume of liquid (1-10 mL). The main difference is that the plate is much smaller, while the walls of the funnel angle outward instead of being vertical. It is named after the German chemist Robert Hirsch (1856-1913).

retardation factor    →   faktor zaostajanja

Retardation factor, R_F, (in planar chromatography) is a ratio of the distance travelled by the centre of the spot to the distance simultaneously travelled by the mobile phase:

The R_F value is characteristic for any given compound on the same stationary phase using the same mobile phase for development of the plates. Hence, known R_F values can be compared to those of unknown substances to aid in their identifications.

thin layer chromatography    →   tankoslojna kromatografija

Thin layer chromatography. (TLC) is a technique for separating components in a mixture on the basis of their differing polarities. A spot of sample is placed on a flat sheet coated with silica and then carried along by a solvent that soaks the sheet. Different components will move different distances over the surface. TLC is a useful screening technique in clinical chemistry; for example, it can be used to detect the presence of drugs in urine.