Method of obtaining complex acidic salts of divalent metals and dicarboxylic acids

A method of obtaining a complex acidic salt of a divalent metal and a dicarboxylic acid, the method comprising:

• heating water in a reactor;
• adding a dicarboxylic acid to the heated water to produce a suspension of the dicarboxylic acid in the water;
• stirring the water to dissolve the dicarboxylic acid in the heated water so as to convert the suspension into a solution of the dicarboxylic acid in the heated water;
• during the stirring, and while the suspension is being converted to the solution, adding MeO to the reactor, where Me is a divalent metal, and
• wherein a molar ratio of the dicarboxylic acid and the MeO in the heated water is 2.005:1-2.1:1;
• continuing the stirring until formation of the complex acidic salt Me(AcH)2.nH2O begins,
• where Ac is an anion of the dicarboxylic acid, and 0<=n<=8;
• cooling the complex acidic salt to below a temperature of crystallization of the complex acidic salt;
• sedimenting the complex acidic salt;
• filtering the complex acidic salt to remove water from the complex acidic salt;
• and
• drying the complex acidic salt.