Sodium Phosphate - Na3PO4

What is Sodium Phosphate?

Sodium phosphate 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.

It is prepared by neutralization of phosphoric acid under controlled conditions with sodium hydroxide or sodium carbonate. 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

Na3PO4 Sodium Phosphate
Density 1.62 g/cm³
Molecular Weight/ Molar Mass 163.94 g/mol
Boiling Point 100 °C
Melting Point 1,583 °C
Chemical Formula Na3PO4

Sodium Phosphate Structure – Na3PO4


Physical Properties of Sodium Phosphate – Na3PO4

Odour Odourless
Appearance Off-white powder
Covalently-Bonded Unit 4
Complexity 36.8
Hydrogen Bond Acceptor 4
Solubility Soluble in water

Chemical Properties of Sodium Phosphate – Na3PO4

    • Sodium phosphate reacts with hydrochloric acid to form phosphoric acid and sodium chloride. The chemical reaction is given below.

Na3PO4 + 3HCl → H3PO4 + 3NaCl

    • Sodium phosphate reacts with calcium chloride resulting 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 the emptying of the gall bladder.
  • One of the most palatable of the saline laxatives. It is also used in the form of an oral solution as an antihypercalcemia.
  • Used to control the pH of water hardness precipitation and control agent in mildly acidic solutions.

Frequently Asked Questions


Is sodium phosphate an acid or a base?

Sodium phosphate is a salt obtained by the reaction of phosphoric acid and sodium hydroxide.


What is sodium phosphate used for in medicine?

Sodium biphosphate and sodium phosphate are sources of phosphorus which is a material that occurs naturally and is essential in every cell in the body. Sodium biphosphate and sodium phosphate is a combination drug used in adults before a colonoscopy to relieve constipation and cleanse the intestines.


What happens if your phosphate levels are low?

High phosphate levels seldom contribute to hypophosphatemia symptoms; rather symptoms generally arise from the underlying disorder that causes hypophosphatemia. Ultra low levels of phosphate can cause difficulty breathing, agitation, altered mental state, muscle weakness and muscle damage called rhabdomyolysis.


What is sodium phosphate monobasic monohydrate?

Sodium Phosphate, monobasic (monohydrate) is a reagent commonly used in molecular biology, biochemistry, and chromatography with a very high buffering capacity. Monobasic sodium phosphate is extremely hygroscopic and soluble in water.


What is the difference between sodium phosphate monobasic and dibasic?

Sodium phosphate monobasic has the chemical formula of NaH2PO4, and the chemical formula of Na2HPO4 has sodium phosphate dibasic. As sodium phosphate dibasic dissolves in water, the basicity in the medium is higher than when monobasic sodium phosphate dissolves in water.


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