CHEMISTRY GLOSSARY

Liebig condenser    →   Liebigovo hladilo

Liebig condenser is used for condensing of vapours that pass trough the centre tube. It is cooled with water that passes in the outer tube (shell around the centre tube) in the opposite direction than the one of hot vapour. Though named after the German chemist Justus von Liebig (1803-1873), he cannot be given credit for having invented it because it had already been in use for some time before him.

Allihn condenser    →   Allihnovo hladilo

Allihn condenser or bulb condenser consists of an outer water jacket and the inner glass tube with a series of spherical bubbles to maximize the thermal contact with the cooling water. It is named after its inventor, the German chemist Felix Richard Allihn (1854-1915).

bulb condenser    →   kuglasto hladilo

See Allihn condenser

reflux condenser    →   povratno hladilo

Reflux condenser is used for repeated transformation of vapour in liquid in order to prevent the loss due to evaporation.

condensed structural formulas    →   kondenzirane strukturne formule

Condensed structural formulas are shortened and easier layout of structural formulas of organic compounds (butane, CH₃(CH₂)₂CH₃).

cryogenic fluid    →   kriogenski fluid

Cryogenic fluids are used for accessing low temperatures, usually below -150 °C. Cryogenic temperatures are achieved by the rapid evaporation of volatile liquids. The most common laboratory cryogenic fluids are liquid nitrogen (-196 °C). Nitrogen gas is colorless and odorless. The cloud formed when pouring liquid nitrogen is condensed water vapour from the air, not nitrogen gas.

fractional distillation    →   frakcijska destilacija

Fractional distillation is a procedure in which liquids of close boiling points are separated. It is conducted in fraction or rectification columns in a way that vapour phase created by distillation is condensed and the condensate thus obtained is redistilled. The procedure is repeated several times. Vapour phase always contains more volatile component than the liquid phase, at top of the column vapour of clean volatile component gets out and at the bottom of the column liquid of nonvolatile component.

Kjeldahl’s method    →   Kjeldahlov postupak

Kjeldahl’s method is an analytical method for determination of nitrogen in certain organic compounds. The method was developed by the Danish chemist Johan Kjeldahl (1849-1900).

It involves addition of a small amount of anhydrous potassium sulphate to the test compound, followed by heating the mixture with concentrated sulphuric acid, often with a catalyst such as copper sulphate. As a result ammonia is formed. After alkalyzing the mixture with sodium hydroxyde, the ammonia is separated by distillation, collected in standard acid, and the nitrogen determined by back-titration.

1. Kjeldahl flask for decomposition (500 ml – macro or 100 ml - micro)
2. funnel for alkaline solution
3. Wagner tube (drop catcher)
4. condenser
5. absorption flask with known volume of standard acid

polychlorinated biphenyls    →   poliklorirani bifenili

Polychlorinated biphenyls (PCB) are poisonous and carcinogenic compounds. They are pollutants of both live and inanimate environment, and they are used as insulation and refrigerating materials in transformers and condensers.

Wilson’s chamber    →   Wilsonova komora

Wilson’s chamber is used for detection of radioactive radiation. Wilson’s chamber has a glass cylinder filled with air that has been saturated with water vapour. Radioactive radiation in its way ionises molecules of gas which then function as centres on which water vapour condenses into very small drops, thereupon showing Tyndall’s effect, i.e. is they are visible as a bright trail.