A vessel is one-quarter-filled with aqueous solutions and sludges, preferably of salty sea water, which is exposed to heat by solar or other forms of radiation. The liquid, evaporated parts are precipitated in the form of condensate onto the walls, which condensate flows off outwards via a duct provided in the vessel. The apparatus for this purpose is composed of a steep-sided vessel, the bottom part of which is designed as a filling chamber and the top part of which is designed as an evaporation chamber. A duct having a gradient is mounted in the lower third of the vessel, the lowest point of which duct ends in a bend which has an inlet curving upwards and an outlet curving downwards which can be optionally opened and closed. The condensation water obtained is made palatable and nutritional for humans and animals by addition of tablets or minerals. If it is to serve for irrigating plants, nutrient salts, etc. are added.
