CHEMISTRY GLOSSARY

Cystine    →   Cistin

Cystine (C6H12N2O4S2) is a dimer of cysteine. It is formed by the oxidation of the thiol groups (-SH) of two cysteines generating a disulphide bridge (-S-S-). Cystine is a white crystalline solid that is slightly soluble in water. Cystine is particularly abundant in skeletal and connective tissues and in hair, horn, and wool.

Heyrovsky-Ilkovic equation    →   Heyrovsky-Ilkovičeva jednadžba

The Heyrovsky-Ilkovic equation describes the entire current-potential curve (polarographic wave) of a reversible redox system in polarography

where R is the gas constant, T is the absolute temperature, F is the Faraday constant, n denotes the number of electrons taking part in the electrode reaction. E_1/2 is a unique potential (for a given reaction and supporting electrolyte) termed the half-wave potential.

In order to obtain E_1/2 from the above equation, we plot a graph of ln[(i_d-i)/i] against E. The intercept on the x-axis gives then an accurate value of E_1/2. The slope of the obtained straight line is equal to nF/RT from which n is determined.