Most of these salts are acted upon by dilute H2SO4 or dilute HCl and concentrated H2SO4 .In each case, a gas is liberated which is characteristic of the particular acidic radical. There are some acidic radicals which are not decomposed either by dilute H2SO4 or concentrated H2SO4 .
Hence, for the identification of the acidic radicals, the following scheme is followed:
Group I: This group consists of radicals which are detected by dilute H2SO4 or dilute HCl.
These are (i) carbonate, (ii) sulphite, (iii) sulphide, (iv) nitrite and (v) acetate.
Group II: This group consists of radicals which are detected by concentrated H2SO4 .
These are (i) chloride, (ii) bromide, (iii) iodide, (iv) nitrate and (v) oxalate.
Group III: The radicals which do not give any characteristic gas with dilute and concentrated H2SO4 .
These are (i) sulphate, (ii) phosphate, (iii) borate and (iv) fluoride.
