Qualitative analysis involves determining the composition of an unknown compound or mixture. Qualitative analysis can also analyze a mixture to determine the precise percentage composition of the sample in terms of elements, radicals, and compounds. Whereas quantitative analysis involves determining how much of a material is present in a sample (quantity), qualitative analysis involves identifying what materials are present in a sample (quality).

Qualitative analysis was the primary method of analysis until the seventeenth century. The alchemists used this method of analyzing substances in their attempts to transmute lead into gold. Robert Boyle was one of the first chemists to perform chemical reactions where one individual substance was differentiated from others by the use of specific reagents. In the eighteenth and nineteenth centuries, analyses based upon the different solubilities of metal ions became a useful way to determine the composition of mixtures. The use of this...