CHEMISTRY GLOSSARY

lecithin    →   lecitin

Lecithin is the popular name for a naturally occurring mixture of phospholipids (phosphatides) which is obtained from seeds (soybeans) and is used as a dispersing agent for fats. Lecithin is admitted by the EU as a food additive, designated by E number E322.

ligroine    →   ligroin

Ligroine is a petroleum derivative with the boiling point from 6 °C-90 °C similar to petroleum ether. It is nonpolar. It is used as a solvent for fats, resins and latex.

lipids    →   lipidi

Lipids are a loosely defined term for substances of biological origin that are soluble in nonpolar solvents. They consist of saponifiable lipids, such as glycerides (fats and oils) and phospholipids, as well as nonsaponifiable lipids, principally steroids.

Gratzel solar cell    →   Gratzelova sunčeva ćelija

Grätzel solar cell is photoelectrochemical cell, developed by Michael Grätzel and collaborators, simulates some characteristics of the natural solar cell, which enables photosynthesis take place. In natural solar cell the chlorophyll molecules absorb light (most strongly in the red and blue parts of the spectrum, leaving the green light to be reflected). The absorbed energy is sufficient to knock an electron from the excited chlorophyll. In the further transport of electron, other molecules are involved, which take the electron away from chlorophyll. In Grätzel cell, the tasks of charge-carrier generation and transport are also assigned to different species.

His device consists of an array of nanometre-sized crystallites of the semiconductor titanium dioxide, welded together and coated with light-sensitive molecules that can transfer electrons to the semiconductor particles when they absorb photons. So, light-sensitive molecules play a role equivalent to chlorophyll in photosynthesis. In Grätzel cell, the light-sensitive molecule is a ruthenium ion bound to organic bipyridine molecules, which absorb light strongly in the visible range; titanium dioxide nanocrystals carry the received photoexcited electrons away from electron donors. On the other hand, a donor molecule must get back an electron, so that it can absorb another photon. So, this assembly is immersed in a liquid electrolyte containing molecular species (dissolved iodine molecules) that can pick up an electron from an electrode immersed in the solution and ferry it to the donor molecule. These cells can convert sunlight with efficiency of 10 % in direct sunlight and they are even more efficient in diffuse daylight.

ion exchanger    →   ionski izmjenjivač

Ion-exchanger is a solid or liquid material containing ions that are exchangeable with other ions with a like charge that are present in a solution in which the material is insoluble. Ion-exchange resins consist of various copolymers having a cross-linked three-dimensional structure to which ionic groups have been attached.

iridium    →   iridij

Iridium was discovered by Smithson Tennant (England) in 1803. The origin of the name comes from the Latin word iris, meaning rainbow, because its salts are highly colored. It is heavy, brittle, white metal. Unreactive in air, water and acids. Attacked by fused NaOH. Metal ignites and burns readily. Iridium is found in gravel deposits with platinum. Used with osmium to tip gold pen points, to make crucible and special containers. Also to make alloys used for standard weights and measures and heat-resistant alloys. Also as hardening agent for platinum.

marl    →   lapor

Marl is a grey or yellow natural mixture of clay and lime in different proportions. It is also used as a raw material in the production of cement.

macromolecule    →   makromolekule

Macromolecule is a molecule of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetitions of units derived, actually or conceptually, from molecules of low relative molecular mass. The types of macromolecules are natural and synthetic polymers, carbohydrates, lipids, proteins etc. Cellulose is a polysaccharide that is made up of hundreds, even thousands of glucose molecules strung together.

neoprene    →   neopren

Neoprene is a synthetic rubber made by polymerising the compound 2-chlorobuta-1,2-diene. Neoprene is often used in place of natural rubber in applications requiring resistance to chemical attack.

ore    →   ruda

Ores are natural mineral aggregates (compounds in which metals are found in nature) from which get one or more metals can be obtained rentably. Except for minerals, ore also contains some other ingredients which do not have any technical value and are usually called waste.