<unk> (II) sulfate or just<unk>  sulfate, usually refers to the chemical compound with the formula NiSO4.6H2O.  This blue salt is a common laboratory source of<unk> .  It also occurs as the rare mineral Retgersite.  The anhydrous salt, NiSO4, a high melting solid, is also known but is less commonly encountered.  These<unk> (II) compounds are paramagnetic.
Nickel
Organonickel
Cilium
Cobalt
Mercury
Mercury 
Lead
Formaldehyde