Summary

When salts dissolved in water, the positively and negatively charged ions in the crystal salt separate and disperse throughout the solution. These ions in solution should be treat individually; some may react with other ions to form a new compound.

Precipitation reactions are used for the identification of positively charged metal ions in solution. Each metal ion reacts in a different way with hydroxide ion (OH^-) to form precipitates of metal hydroxide and these tests provide a means of identifying which metal is present in an unknown sample. Qualitative data from reactions of metal ions with sodium hydroxide solution is usually similar (but not always) to observations from reactions of metal ions with ammonia solution; any similarities and/or differences can be important clues to the identification some metal ions.

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