Acidity and basicity of compounds are indications of the pH. Acidity of a medium is caused by acidic compounds, which can release hydrogen ions (H+), resulting in a low pH in that medium.

Salicylic acid is a fat soluble organic acid with the chemical formula c7h6o3. The appearance is white crystalline powder, and the melting point is 158 ~ 161 ℃. It exists in willow bark, white pearl leaves and sweet birch in nature.