Process for isolating H acid and K acid

摘要

The invention relates to a process for isolating H acid and K acid in the form of their monoalkali metal salts from acid aqueous solutions which contain these two acids and alkali metal ions and may contain other aminonaphtholdisulphonic acids, in which process H acid monoalkali metal salts are precipitated at elevated temperatures from solutions which contain not only sodium ions but also potassium ions and then precipitating K acid monoalkali metal salts by cooling down the filtrate obtained after separating off the H acid monoalkali metal salts.