Sodium Phosphate - Na3PO4

What is Sodium Phosphate?

Sodium phosphate is also known as phospho soda with the formula Na3PO4 is a saline cathartic that is familiar to radiologists since it is often used as a cleansing agent prior to double contrast barium enema. Sodium phosphate cradles are the most widely recognized, yet there is broad utilization of potassium phosphate buffer and blends of sodium and potassium. Many compounds of pharmaceutical interest are formulated in sodium phosphate buffers.

Other names – Trisodium phosphate, Sodium orthophosphate, Tribasic sodium phosphate


Sodium Phosphate


1.62 g/cm³

Molecular Weight/ Molar Mass

163.94 g/mol

Boiling Point

100 °C

Melting Point

1,583 °C

Chemical Formula


Sodium Phosphate Structure – Na3PO4

Sodium Phosphate Structure

Physical Properties of Sodium Phosphate – Na3PO4




Off-white powder

Covalently-Bonded Unit




Hydrogen Bond Acceptor



Soluble in water

Chemical Properties of Sodium Phosphate – Na3PO4

  • Sodium phosphate reacts with hydrochloric acid forms phosphoric acid and sodium chloride. The chemical reaction is given below.
  • Na3PO4 + 3HCl → H3PO4 + 3NaCl

  • Sodium phosphate reacts with calcium chloride results in the formation of calcium phosphate and sodium chloride. The chemical reaction is given below.
  • 2Na3PO4 + 3CaCl2 → 6NaCl + Ca3(PO4)2

Uses of Sodium Phosphate – Na3PO4

  • Short-term, local treatment of inflammation with neomycin as bacterial prophylaxis.
  • Used after glaucoma surgery or after cataract surgery.
  • Used as a mild laxative, stimulates emptying of gall-bladder.
  • One of the most palatable of the saline laxatives. It is also used in the form of the oral solution (see below) as an antihypercal- cemic.
  • Used to control the pH of water hardness precipitation and control agent in mildly acidic solutions.

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