Anhydrous monobasic sodium phosphate is a chemical compound obtained by the reaction of phosphoric acid with sodium sources and is Sodium phosphate monobasic without water.

The name describes the structure of the molecule:

• Anhydrous indicates that the compound is without water (anhydrous). Anhydrous compounds are often more concentrated and reactive compared to their hydrated forms.
• monobasic specifies that the sodium phosphate is in the monobasic form, meaning it has replaced only one hydrogen of phosphoric acid.
• sodium phosphate. This part of the name indicates that the compound is a sodium salt of phosphoric acid. Sodium phosphate is known for its buffering properties and as a pH regulator.

Raw Materials and Their Functions

Phosphoric Acid. A mineral acid used as a reagent to form monobasic sodium phosphate.

Sodium. An alkaline chemical element used to neutralize phosphoric acid and form the sodium salt.

Industrial Chemical Synthesis of Anhydrous Monobasic Sodium Phosphate

• Neutralization. The process begins with the reaction of phosphoric acid with a sodium base, such as sodium hydroxide or sodium carbonate.
• Reaction Control. The reaction is monitored to ensure that the ratio of phosphoric acid to sodium is correct and that the desired salt is formed.
• Drying. After the reaction, monobasic sodium phosphate is dried to remove water and obtain the anhydrous form.
• Purification. The anhydrous monobasic sodium phosphate is purified to remove impurities and by-products.
• Quality Control and Packaging. Anhydrous monobasic sodium phosphate undergoes quality checks to ensure it meets the required standards. After quality control, it is packaged for use in sectors such as the food industry, pharmaceuticals, and as an additive in detergents and cleaning products.

It appears as a white crystalline powder soluble in water and acid water, insoluble in ethanol. 

What it is used for and where

Anhydrous Monobasic Sodium Phosphate is used as a food additive, in medicine for preparing dialysis solutions, and in the laboratory as a chemical reagent.

Human nutrition

Monobasic sodium phosphate is commonly used for oral phosphorous supplementation.

In the food and fermentation industry it functions as a buffering agent, a raw material in yeast powder, an adhesive and curing agent for bread and condiments. Improves appearance and quality as an acid agent in evaporated milk. Stabilising agent in cheese and other dairy products, meat, stabiliser in fish products, binder, buffer in yeast.

As a leavening agent it controls the speed of product fermentation, reduces rehydration time and prevents stickiness.

In the production of baked goods, cracker cakes can reduce fermentation time, extend shelf life.

Animal feeding

Sodium phosphate monobasic is commonly used for oral phosphorous supplementation.

In animal feed production, it is used as a source of phosphorous for fish and shrimp feed, as its solubility in water allows phosphorous to be fully utilised by aquatic fish and shrimp, reducing the cost of aquaculture and water pollution caused by phosphorous loss in the aquaculture process, thus meeting environmental protection requirements.

Medical

Together with dibasic sodium phosphate, it is used in adults and children in evacuative solutions such as disposable enemas for the treatment of constipation, the treatment of acute and chronic constipation and also for colon cleansing as preparation for surgical procedures (1). These chemical compounds increase the water content and volume of stools, creating a rectal distention effect. The required effect is usually produced within about 5 minutes.

Other uses

Used in the manufacture of household detergents, metal cleaners, colour additives and pigment precipitators.

Adjuvant in boiler water treatment by electroplating (covering non-precious metals with a light layer of precious metal).

Acidity buffer, excipient in mica processing.

Raw material for the production of sodium hexametaphosphate and polypolyphosphate.

Safety

EFSA's Scientific Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids issued a safety assessment of monosodium phosphate considering it safe when used for long-term storage and/or hot-filling up to 95 °C (2).

Anhydrous sodium phosphate monobasic studies

Typical commercial product characteristics MonoSodium Phosphate

Appearance	White crystal or crystalline powder
pH	4.1-4.7
Boiling Point	100°C
Melting Point	<0ºC
Density	1.40 g/mL at 20°C
PSA	90.40000
Water Insoluble	≤0.2%
Loss on Drying	≤2.0%
Phosphorous	25.3~26.6
As	≤0.001%
Lead	≤0.003%
Fluoride	≤0.02%
Sulphates	≤2.0%
Chromium	≤0.003%
Safety

Price

100g    €31.50

1kg      €104.00

• Molecular Formula NaH₂PO₄     H₂NaO₄P    
• PMolecular Weight    119.977
• Exact Mass    119.958839
• CAS  7558-80-7
• UNII    KH7I04HPUU
• EC Number   231-449-2    231-558-5
• DSSTox Substance ID  DTXSID7035222
• IUPAC  sodium;dihydrogen phosphate
• InChI=1S/Na.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+1;/p-1 
• InChl Key      AJPJDKMHJJGVTQ-UHFFFAOYSA-M
• SMILES   OP(=O)(O)[O-].[Na+]
• MDL number  MFCD00003527
• PubChem Substance ID    24899443
• ChEBI  37585
• RXCUI        349753
• eCl@ss       38070208
• RTECS   WA1900000

Synonyms

• sodium dihydrogenphosphate
• Sodium dihydrogen (16O4)phosphate
• Sodium dihydrogenorthophosphate

References_____________________________________________________________________

(1) Osgard E, Jackson JL, Strong J. A randomized trial comparing three methods of bowel preparation for flexible sigmoidoscopy. Am J Gastroenterol. 1998 Jul;93(7):1126-30. doi: 10.1111/j.1572-0241.1998.00342.x. 

(2) EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF). (2013). Scientific Opinion on the safety evaluation of the active substances, iron, polyethyleneglycol, disodium pyrophosphate, monosodium phosphate and sodium chloride for use in food contact materials. EFSA Journal, 11(6), 3245.