Density and Concentration: The density of 85% phosphoric acid is typically around 1.685 g/mL at 25°C, with a molar concentration of approximately 14.6–14.8 mol/L. Some data sources may report a density as high as 1.874 g/mL, but this usually refers to anhydrous phosphoric acid or values under specific conditions. For commercially available 85% solution, the density of 1.685 g/mL is more commonly accepted.

Melting Point and Crystallization: The melting point of pure phosphoric acid is 42.35°C. However, the 85% phosphoric acid solution is prone to crystallization at low temperatures, with a freezing point of approximately 21°C. The risk of crystallization increases significantly when the ambient temperature drops below 4°C.

Boiling Point and Stability: The boiling point is approximately 158°C (with decomposition). When heated to 213°C, it dehydrates to form pyrophosphoric acid, and above 300°C it converts to metaphosphoric acid.

Appearance and Odor: A colorless, transparent or slightly colored viscous liquid, odorless, with strong hygroscopicity and corrosiveness.

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Where is it mainly used?

Agricultural Production: It is a key raw material for the production of phosphate fertilizers (such as superphosphate and potassium dihydrogen phosphate) and feed nutrients (such as dicalcium phosphate), promoting crop growth and animal bone development.

ndustrial Processing: It is used for metal surface phosphating, rust removal, electropolishing, as well as in the manufacture of zinc phosphate dental cements, refractory mortars, and other related products.

Chemical Reagent: In the laboratory, it is used as a medium-strength tribasic acid for preparing buffer solutions, catalysts, or desiccants.

Storage Conditions: It should be stored in a cool, well-ventilated area, away from alkalis and metal powders. In low-temperature environments, precautions should be taken to prevent crystallization. If crystallization occurs, it can be redissolved by heating in a warm water bath.