Qualitative analysis of inorganic salts and mixtures is an essential experiment carried out in high school, undergraduate, and postgraduate levels all over the world especially in India and South Asia. The classical technique uses H2S, which is highly toxic and has adverse effects on humans and the environment. Increasing awareness concerning a healthy environment has prompted us to develop a green scheme for detection of cations. NH4+ and K+ are detected directly in group zero. Pb2+ and Ag+ are detected in group I as chlorides using dilute HCl. Ca2+, Sr2+, Ba2+, and Pb2+ are precipitated in group II as sulfates using Na2SO4(aq) and ethanol. Cu2+, Cd2+, Fe3+, Mn2+, Co2+, Ni2+, and Mg2+ are precipitated as hydroxides using NaOH and H2O2 in group III. The precipitate is treated with NH3(aq) leaving a residue (group IIIA: Fe3+, Mn2+, Mg2+ as hydroxides) and the centrifugate (group IIIB: Cu2+, Cd2+, Ni2+, Co2+ as soluble ammines). Al3+, Zn2+, Sn2+/Sn4+ (as soluble hydroxo complexes), and Cr3+ (as CrO42-) are detected in group IV, in the presence of each other by using selective reagents. The separation is sharp; individual cations are detected by spot tests and conventional methods. This scheme is simple and fast and makes green chemistry accessible to students.
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