The mineral water is unique in Europe, bursts to the surface from as deep as 50-70 m, with an average temperature of 62.5°C. Its mineral content is about 1000 mg per litre. From a medical point of view, its most important component is carbon sulphide, which is under pressure, dissolved in water in a gaseous state. A compound having bivalent sulphur, carbon sulphide (COS), which, as a gas, is in solution and under pressure in the water. When the water comes to the surface, the gas is released from under pressure and immediately begins to decompose, it turns into hydrogen sulphide gas, which gives the characteristic scent of the medicinal water of Harkány. In a side-light, the precipitated tiny grains of elementary sulphur can be plainly observed in the ponds. Approximately 12 mg carbon sulphide can be found in 1 litre of water.
By the way, this compound had not been known before, it was discovered here during the chemical analysis of the water in the 1860s. It is very actively absorbed both through the skin and via breathing: its absorption is 150 times as effective as that of tetravalent sulphuric compounds.