Potassium hydrosulfuric acid ($KHSO_ {4} $) is mixed with lithium acetate ($LiCH_ {3} COO $). Potassium hydrosulfuric acid in water dissociates into potassium ions ($K ^{+}$）、 hydrogen ions ($H ^ {+} $) and sulfate ions ($SO_ {4} ^ {2 - }$）； lithium acetate in water, and also dissociates into lithium ions ($Li ^ {+} $) and acetate ions ($CH_ {3} COO ^{-}$）。

Hydrogen ion ($H ^ {+} $) is active, and when acetate ion ($CH_ {3} COO ^{-}$）， combine into acetic acid ($CH_ {3} COOH $). Capsular acetic acid is a weak acid and is difficult to fully dissociate in water.

The net ion reaction formula is: $H ^{+} + CH_ {3} COO ^ {-}\ rightleftharpoons CH_ {3} COOH $. Among them, potassium ions ($K ^ {+} $) and sulfate ions ($SO_ {4} ^ {2 - }$）、 lithium ions ($Li ^ {+} $) do not participate in the substantial change, but are only ions from the sidelines. Looking at this reaction, it can be seen that the chemical change, the interaction between ions, is very subtle, which is a wonderful principle of nature.