The following is a simple summary of some rules that can be used to predict solubility. A salt listed as insoluble will always have some level of solubility but it will be exceedingly small. Therefore the terms insoluble and slightly soluble are interchangeable.

Generally speaking precipitates that form will be colorless unless they contain a transition metal ion, either as the cation or as part of the anion. A notable exception is Ag⁺ which tends to be colorless

I. Nitrates:

• Most Nitrate (NO₃^1-) salts are soluble
  

 

II. Alkali Metals (group 1) and Ammonium (NH₄¹⁺) ions:

• Most salts of these ions are soluble

 

III. Halides:

• Most salts of Cl^-, Br^-, I^- are soluble
• EXCEPT:
  • Ag⁺
  • Pb²⁺
  • Hg₂²⁺

IV. Sulfates:

• Most salts of SO₄^2- are soluble
• EXCEPT:

• Ba²⁺
• Ca²⁺
• Pb²⁺
• Hg²⁺, Hg₂²⁺

V. Hydroxides:

• Group I (e.g. Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ ) hydroxides (OH^-) are soluble
• Group II Hydroxides of Ba²⁺, Ca²⁺, and Sr²⁺ are marginally soluble
• All others are Insoluble

VI. Others:

• S^2- (sulfide), CO₃^2- (carbonate), CrO₄^2- (chromate) and PO₄^3- (phosphate)
• Group I and Ammonium salts are soluble
• All others are Insoluble

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Created 08/12/01
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