The interest of man in the role of water in his life dates back to 700–600 b.c. Water is an indispensable part of any life on the earth. Various kinds of suggestions were made concerning the nature and the properties of water in the course of more than two thousand years. Only in the eighteenth century M. Lomonosov gained a penetrating insight into the chemical problems of that time and brought chemistry to the level of science dealing with the composition and qualitative changes of natural substance. He suggested that river wafers were solutions of salts discharged into the sea.