iron alum

noun

Definition of iron alum

1 : an alum containing iron as the trivalent constituent especially : ammonium ferric alum NH4Fe(SO4)2.12H2O
2 [alum entry 1 (aluminum sulfate)] : halotrichite

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“Iron alum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/iron%20alum. Accessed 29 May. 2020.

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