Insoluble Compounds Contain (usually do NOT dissolve in water)

CO₃^2-

Carbonate - insoluble except with alkali metals or NH₄⁺

PO₄^3-

Phosphate - insoluble except with alkali metals or NH₄^-

S^2-

Sulfide - insoluble except with alkali metals, NH₄⁺, Ca²⁺, Sr²⁺, Ba²⁺

OH^-

Hydroxide - insoluble except with alkali metals, NH₄⁺, Ca²⁺, Sr²⁺, Ba²⁺

CrO₄^2-

Chromate- insoluble except with alkali metals or NH₄⁺

SO₃^2-

Sulfite - insoluble except with alkali metals or NH₄⁺

Ag⁺

silver - insoluble except with CH₃COO⁻, NO₃⁻, ClO₃⁻, or ClO₄⁻

Hg₂²⁺

Mercury (I) - insoluble except with CH₃COO⁻, NO₃⁻, ClO₃⁻, or ClO₄⁻

Pb²⁺

lead (II) - insoluble except with CH₃COO⁻, NO₃⁻, ClO₃⁻, or ClO₄⁻