Yellow-green toxic and pungent smelling gas (Cl) or element. The name (chlôrós = green) is derived from the yellow-green colour of chlorine gas. Due to its reactivity it does not occur in nature in elemental form, but mainly in the form of salts as sodium chloride (table salt) and potassium chloride. As a nutrient, it is only needed by the vine in small quantities, if at all. A deficiency in the vineyard hardly ever occurs. Young vines in particular react very sensitively to a not so rare surplus with a reduction in yield. For this reason, potassium chloride fertilization in the form of potassium chloride (two-substance fertilization) should only be applied in very small doses or in the form of potassium sulfate. Organic chlorine compounds are harmful to health and especially toxic for insects and are therefore used as insecticides.