Quantitative analysis: tests for ions GapFill

Metal ions can be identified using flame tests, which involve burning a metal compound in a Bunsen burner and observing the distinctive colour of the flame. For example, lithium ions burn  blackbrowngreenred,while calcium ions burn  goldwhiteoliveorange-red. Many ions can also be identified from the colour of the  watercrystalprecipitatesolution which forms when the metal reacts with sodium hydroxide:

• Calcium ions:  colourlessfawnwhitesilver, and does not redissolve when more sodium hydroxide is added
• Aluminium ions: white, and dissolves when more sodium hydroxide is added
• Copper(II): blue
• Iron(II):  orangemauvepinkgreen
• Iron(III):  brownredsilvergreen

There are also qualitative tests for anions:

• Carbonate ions give off carbon dioxide when a dilute acid is added.
•  ChlorideNegativeNitrateSulfate ions form a white precipitate with barium chloride in hydrochloric acid.
• Halides form coloured precipitates when  potassium sulfatelead chloridemagnesium chloridesilver nitrate is added. The colour of the precipitate depends on the halide, e.g.  fluoridebromideiodidechloride goes yellow.

 OpticalVisualExperimentalInstrumental methods are more accurate, more sensitive and quicker than chemical methods. One example is flame photometry, where metal ions are put through a flame and a  precipitatetable of dataspectrumlogarithm is produced.