For flotation of iron ores by fatty acids (tall oil) in the conditions of the Krivoy Rog basin influence of salt composition of water on flotation is of particular importance, as the technical water of enrichment plants is diverse in its composition and has a high hardness. Changing the composition of water under the action of lime, soda and caustic soda is reduced to its softening. The pH required for sufficiently complete softening is determined, according to I.E. Apeltsin, depending on the initial hardness, general salinity, temperature, time, and final hardness. Fig. 1 shows that by joint action of lime with soda and caustic soda with caustic soda the hardness of the technical water of CGOK is reduced.