Monosodyum Fosfat, Monosodium Phosphate, Sodium Acid Phosphate, Sodium Biphosphate, Sodium Dihydrogen Phosphate, MAP, 7558-80-7

Monosodyum Fosfat, Monosodium Phosphate, Sodium Acid Phosphate, Sodium Biphosphate, Sodium Dihydrogen Phosphate, MAP, 7558-80-7

MONOSODIUM PHOSPHATE (MSP)

1. PRODUCT DEFINITION AND CHEMICAL IDENTITY

Note: Monosodium phosphate is a monobasic sodium salt of phosphoric acid containing a single sodium atom. It is commercially available in anhydrous and dihydrate forms, as well as in technical and food/pharmaceutical grades.

2. PHYSICAL AND CHEMICAL PROPERTIES

3. FUNCTIONAL PROPERTIES

• pH Control / Acidulant: Provides a mildly acidic pH (~4.5 in solution), making it an effective acidity regulator in food, pharmaceutical, and industrial applications.

• Buffering Agent: Forms buffer systems when combined with its conjugate base (disodium phosphate), helping maintain a stable pH in formulations.

• Sequestrant / Metal Ion Control: Reacts with metal ions (e.g., lead, calcium, magnesium) to form insoluble phosphate coatings or soluble complexes, preventing corrosion and scale formation.

• Binding Agent: Acts as a binder in food products and pharmaceutical tablets.

• Halogen Neutralization: Used in waste treatment to neutralize and remove halogenated compounds.

• Urinary Acidifier: In animal feed, helps acidify urine to prevent urinary calculi.

4. ALTERNATIVE NAMES AND SYNONYMS

• Monosodium Phosphate (MSP)

• Sodium Dihydrogen Phosphate

• Sodium Acid Phosphate

• Monosodium Dihydrogen Phosphate

• Sodium Biphosphate

• Sodium Dihydrogen Orthophosphate

• Monobasic Sodium Phosphate

• Primary Sodium Phosphate

• Anhydrous / Dihydrate (form specification)

5. PRODUCT GRADES AND SPECIFICATIONS

6. SECTORAL APPLICATIONS AND USAGE RATES

Example Formulations:

• Effervescent Powder Base (Pharmaceutical):

  • Monosodium phosphate (anhydrous): 30%

  • Sodium bicarbonate: 40%

  • Citric acid: 25%

  • Active ingredient + sweetener + flavour: 5%
    Mix thoroughly; protect from moisture. Upon addition to water, MSP provides the acidic component for effervescence.

• Lead Corrosion Control (Water Treatment):

  • Monosodium phosphate stock solution: 5–10%

  • Dose to achieve 1–3 ppm orthophosphate (PO₄) residual in the distribution system.

  • MSP reacts with lead ions and pipe surfaces to form a protective, insoluble lead-phosphate layer.

• Acid Metal Cleaner:

  • Phosphoric acid (75%): 15%

  • Monosodium phosphate: 3% (pH buffer)

  • Non-ionic surfactant: 2%

  • Corrosion inhibitor: 0.5%

  • Water: 79.5%
    MSP helps maintain a consistent acidic pH for effective cleaning without excessive metal attack.

7. ALTERNATIVES AND COMPARISON

8. REGULATORY STATUS AND SAFETY

• GHS Classification: Not classified as a hazardous substance or mixture under CLP. May cause mild eye and skin irritation upon prolonged contact.

• Food Additive: Approved as E339i (Monosodium phosphate) in the EU; GRAS by FDA (21 CFR 182.1778).

• Pharmaceutical: Listed in USP/EP monographs for sodium dihydrogen phosphate.

• Water Treatment: Approved for use in drinking water treatment under NSF/ANSI Standard 60 (when certified grade is used).

• Storage: Store in a tightly closed container in a cool, dry, and well-ventilated area. Protect from moisture (slightly hygroscopic). Avoid contact with strong bases and oxidizers.

• Personal Protection: Use protective gloves and safety goggles when handling large quantities. Avoid breathing dust.

• Environmental: Phosphates can contribute to eutrophication in surface waters; avoid release to the environment in concentrated form.

9. FREQUENTLY ASKED QUESTIONS

Q1. What is the difference between monosodium phosphate and disodium phosphate?
MSP (NaH₂PO₄) is monobasic and gives an acidic solution (pH ~4.5). DSP (Na₂HPO₄) is dibasic and gives an alkaline solution (pH ~9). They are often used together to form phosphate buffer systems at neutral pH.

Q2. Is monosodium phosphate safe for food use?
Yes, it is an approved food additive (E339i) used as an acidity regulator, binder, and phosphate source in many processed foods. It is GRAS (Generally Recognized As Safe) by the FDA.

Q3. How does MSP prevent lead corrosion in water pipes?
When added to drinking water, MSP dissociates and the phosphate ions react with lead ions and the pipe surface to form a highly insoluble lead-phosphate coating. This protective layer prevents lead from leaching into the water.

Q4. What is the difference between anhydrous and dihydrate forms?
The anhydrous form (NaH₂PO₄) has a molecular weight of 119.98 g/mol. The dihydrate form (NaH₂PO₄·2H₂O) contains two water molecules and has a molecular weight of 156.01 g/mol. The dihydrate is more common for general use; the anhydrous form is preferred when water content must be minimized.

Q5. Does MSP emit fumes when heated?
Yes, when heated to decomposition (~200 °C), MSP emits hazardous fumes including phosphoric acid vapours and sodium oxide. Adequate ventilation is essential when handling hot MSP solutions.

10. QUICK REFERENCE TABLE