oxylic acids such as malonic acid, maleic acid or furmaric acid, or with hydroxycarboxylic acids such as tartaric or citric acid, or with sulfonic acids such as lower alkanesulfonic acids or benzenesulfonic acids or substituted benzenesulfonic acids such as methane or p-toluenesulfonic acid, or salts with bases, typically alkali metal or alkaline earth metal salts, e.g. sodium, potassium or magnes