The Kurnakov test, also known as Kurnakov's reaction, is a chemical test devised by Soviet chemist Nikolai Semenovich Kurnakov. It utilizes the phenomenon of the trans effect to distinguish the pairs of cis- and trans-isomers of square complexes of [PtA2X2] (A=NH3, X=halogen or acid radical) type by treating them with thiourea. It is commonly used in platinum mining.
Uses
Kurnakov test is used to distinguish between cisplatin and transplatin. In hot aqueous solution, the cis compound reacts with aqueous thiourea to give a deeper yellow solution from which yellow needles of tetrakis (thiourea) platinum(II) chloride deposit on cooling, while the trans compound gives a colourless solution from which snow white needles of trans-bis(thiourea)diaammineplatinum(II) deposit on cooling.