Potassium /pəˈtæsiəm/– (Arab. Al-kali – alkali K2CO3 – from the long-known K. compound) – chemical element, symbol K. (lat. Kalium), at.n. 19, at.m. 39.098 K. – silvery white, light, soft and easily soluble metal; belongs to the group of alkali metals. Density 862 kg/m3, liquid=63.55oC. It oxidizes quickly in air. Widely distributed in nature in the form of compounds, the most important of which are sylvin, sylvinite, carnallite minerals, etc. potassium salts. K. is necessary for plant nutrition; of salts 90% are used as potassium fertilizers. K. metal itself is obtained in small quantities in the industry; its use is limited (KO2 used for oxygen regeneration in submarines; K. – Na alloys, which act as heat carriers in nuclear reactors, are produced.)