EXP 7

• GROUP II: The cations of this group do not react with hydrochloric acid (they are chloride soluble ions), and consequently they are readily separated from the slightly soluble Group I cations by forming precipitates with hydrogen sulfide in dilute mineral acid medium.
• group II is further separated into groups through selective precipitation of a number of sulfides. Ions of this group are mercury(II), copper(II), bismuth(III), cadmium (II), tin(II), tin(IV), arsenic(III), arsenic(V), antimony(III), and antimony(V).
• mercury(II), copper(II), bismuth(III), cadmium (II) are sub-group IIA, the sulfides of cations in Group IIA are insoluble in ammonium polysulfide
• tin(II), tin(IV), arsenic(III), arsenic(V), antimony(III), and antimony(V) are sub-group IIB are soluble in ammonium polysulfide
• GROUP III: Cations of this group do not react either with dilute hydrochloric acid, or with hydrogen Sulfide in dilute mineral acid medium. However, they form precipitates with ammonium sulfide in

  neutral or ammoniacal medium.
• Group III are iron(II), iron(III), cobalt(II), nickel(II), manganese(II), chromium(III), aluminium(III), and zinc(II).