Start with rule 1 and work your way down. The first rule that applies to your compound defines your compound.
- Inorganic acids (those not containing carbon, hydrogen, and oxygen) are soluble. Low molecular mass organic acids are soluble.
- Compounds containing alkali metals and ammonium (NH4+) cations are soluble.
- Compounds containing nitrates (NO3–), acetates (C2H3O2–), and perchlorates (ClO4–) are soluble.
- Compounds containing chlorides (Cl–) are soluble except for AgCl, PbCl2 and Hg2Cl2. Compounds containing bromides (Br–) and iodides (I–) have solubility similar to chlorides.
- Sulfate (SO42-) containing compounds are soluble except for PbSO4 and BaSO4. CaSO4 and Ag2SO4 are slightly soluble.
- Hydroxides (OH–) are insoluble.
- Carbonates (CO32-), phosphates (PO43-), and arsenates (AsO43-) are insoluble.
- Sulfides (S2-) are insoluble.