Fe(NH4)2(SO4)2 + 4NaOH → Fe(OH)2 + 2Na2SO4 + 2(NH3•H2O)
Diammonium-iron(II) sulfate react with sodium hydroxide to produce iron(II) hydroxide, sodium sulfate and ammonium hydroxide. Sodium hydroxide - diluted solution. This reaction takes place in a nitrogen atmosphere.