Citric acid, being tribasic, forms either acid monometallic, acid dimetallic or neutral trimetallic salts; thus, mono-, diand tri-potassium and sodium citrates are known.
If the heating be with charcoal, the trimetallic salts of the alkalis and alkaline earths are unaltered, whilst the monoand di-salts give free phosphorus and a trimetallic salt.
The monometallic salts are strongly acid, the dimetallic are neutral or faintly alkaline, whilst the soluble trimetallic salts are strongly alkaline.