what is the basicity of orthophosphoric acid ?Write the types of salts formed by it 

Orthophosphoric acid, H₃PO₄  has three - OH groups and its basicity is 3 
 

Orthophosphoric H₂PO₄ forms three types of salts ${\mathrm{H}}_2{\mathrm{PO}}_4-$ is the anion of primary salt, an acidic salt. ${{\mathrm{HPO}}_4}^2-$ is the anion of secondary salt, an acidic salt ${{\mathrm{PO}}_4}^{3-}$ is the anion of tertiary salt, normal salt.