Precipitation of carboxylates themselves is included here under
primary recovery and the removal of counterions of carboxylates is
dealt with in a later section. A soluble carboxylic acid HA or soluble
carboxylate such as NaA is converted into an insoluble carboxylate by
performing a double replacement reaction. The main example is the
primary recovery of citric acid (H3A),which is precipitated as its calcium
salt with calcium hydroxide: