What is the drying temperature for ammonium ferrous sulfate? At what degree should it be dried?
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When using ammonium ferrous sulfate as an iron ion standard, at what temperature should the reagent be dried without damaging its original components?
Ammonium ferrous sulfate is a double salt, and some of its crystal water is in a coordinated form; therefore, treating it by heating and drying may not be the best approach. You can check the phase diagram of ammonium ferrous sulfate to find the temperature at which the complexed form retains its crystalline water. However, due to dehydration during heating, ammonium ferrous sulfate is exposed to oxygen in the air, which leads to the formation of small amounts of ferric compounds. Since it is converted into ferrous sulfate and sulfuric acid after dehydration, rather than remaining in a double salt form, its stability in the presence of chloride is very poor.