Thiocyanates

THIOCYANATES (from the Greek rhodon-rose, since thiocyanate salts of iron are red in color). Chemical formula CNS or CyS. From thiocyanic acid CNSH, two isomers are theoretically possible: G^N

C = S |

and

|| SH

NH thiocyanic acid

isothiocyanic acid Only the first form is known in the free state. Of the salts of thiocyanic (rhodanic, thiocyanic) acid, the most well-known in medical practice are potassium thiocyanate (KCNS) and ammonium thiocyanate (NH₄CNS). Potassium thiocyanate - colorless, hygroscopic, deliquescent crystals; soluble in water and alcohol. The most characteristic property of KCNS (and NH₄CNS) is its reaction with solutions of ferric salts [formation of ferric thiocyanate, Fe(CNS)₃], in the presence of which even traces the liquid turns pink; with higher concentrations, a blood-red coloration is obtained; when shaken with ether, the color also passes into the ether layer. A very sensitive test for ferric salts (ferrous salts, free from ferric salts, give no coloration).-Ammonium thiocyanate, a crystalline powder, readily soluble in water; like potassium thiocyanate, it serves as a reagent for ferric salts.-Thiocyanates have been found in the blood, in extracts from the liver, pancreas, kidneys, thyroid gland, as well as in urine, feces, nasal secretions, and especially in saliva. Licchint gives an exhaustive literature on the metabolism of thiocyanate substances. The amount of thiocyanates in the blood is determined by Schreiber's method. To the clear blood filtrate, obtained after protein precipitation, a reagent containing iron salts is added. The color is measured in an Autenrit apparatus. The amount of thiocyanates in urine (see) is determined by the method of Edinger and Clemens. Qualitative tests for thiocyanates in saliva are based on the formation of Fe(CNS)₃.-Thiocyanate compounds have been repeatedly proposed as medicinal agents and others.