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9-1 Chemistry/Identification of ions
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Flame tests can be used to identify some cations (positive ions).
Flame tests
+ Compound colour of flamePhoto Lithium Crimson flamecenter|frameless|171x171pxSodiumYellow flamecenter|frameless|151x151pxPotassiumLilac flamecenter|framelessCalciumOrange-red flamecenter|frameless|243x243pxCopperGreen flamecenter|frameless|200x200px
If a sample containing a mixture of ions is used, some flame colours can be masked.
Metal hydroxides
Sodium hydroxide solution can be used to identify some cations:
Aluminium
Calcium
Magnesium
Ions form white precipitates when sodium hydroxide solution is added but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution.