Ion testing is conducted by observing sedimentation, gas evolution, and color changes. For different anions and cations, appropriate salt solutions or alkali solutions can be selected for conversion, and then distinguished based on the solubility, color, and other characteristics of the sedimentation. If there are unstable acid radicals in the solution, acid solution can be added to convert them into gas, thereby determining the type of ions. For solutions that may contain H+, OH-, Fe3+, etc., color indicators such as litmus, phenolphthalein, or thiocyanate can be added to test by observing color changes.