Calcium Phosphate
Properties
| State | Solid at room temperature |
| Color | White amorphous powder |
| Solubility | Insoluble in water; soluble in dilute acids |
| Melting Point | 1670 °C |
About Calcium Phosphate
Calcium phosphate is the structural mineral of vertebrate biology — about 70% of bone dry mass and 96% of tooth enamel — though the in vivo form is actually the closely related hydroxyapatite Ca10(PO4)6(OH)2, with carbonate substitutions and a defective lattice that lets it remodel under osteoclast and osteoblast control. Pure Ca3(PO4)2 (β-TCP, β-tricalcium phosphate, the rhombohedral phase) is the synthetic stand-in. Its solubility product Ksp is around 2 × 10⁻²⁹, which is why bones don't dissolve in body fluid at physiological pH 7.4, and why the same lattice does dissolve when local pH drops — caries-causing oral bacteria push tooth-surface pH below the critical value of about 5.5 and the apatite demineralizes; the CaPO4-fluoride substitution that gives fluorapatite raises that critical pH to about 4.5, which is the molecular basis for fluoride dental treatment. Industrially, β-TCP and biphasic CaP ceramics (β-TCP plus hydroxyapatite) are the most widely studied bone-graft substitutes — they are osteoconductive, meaning bone cells migrate onto and resorb the scaffold while replacing it with new mineralized matrix. The compound is also the entry point to the global phosphorus economy: phosphate rock (mostly fluorapatite-bearing) is treated with sulfuric acid to give phosphoric acid plus gypsum (the wet-process route), and the resulting H3PO4 fans out into fertilizers, detergents, food acidulants, and lithium iron phosphate battery cathode precursors.
Where you'll encounter it
An orthopedic surgeon will hand you a vial of porous β-TCP granules during a bone graft procedure — packed into a tibial defect, the synthetic ceramic gets resorbed by osteoclasts over 6–18 months while new bone fills in. A dentist working on a fluoride varnish appointment is exploiting the same Ca-P chemistry, just with an F⁻ substitution to make the enamel less acid-soluble. In a food plant, tricalcium phosphate at 0.2–1% is the white powder added to powdered sugar, table salt, and grated parmesan to keep them flowing through the auger instead of caking up — its very fine particles coat the bulk granules and physically prevent humidity bridging. In a fertilizer complex, the entire Ca3(PO4)2-derived industry runs through 'normal superphosphate' and 'triple superphosphate' production, where rock phosphate plus sulfuric acid yields water-soluble Ca(H2PO4)2 plus gypsum.
Common Uses
- Synthetic bone-graft substitute as porous β-TCP or biphasic β-TCP/hydroxyapatite scaffold
- Anti-caking agent (E341) at 0.2–1% in powdered sugar, salt, and dry seasonings
- Calcium fortifier in soy milk, almond milk, and breakfast cereals
- Animal feed mineral supplement for poultry, dairy, and aquaculture
- Phosphate rock starting material for the wet-process H3PO4 industry
- Carrier and binder in pharmaceutical tablet formulations
- Bone-replacement scaffold in dental implants and craniofacial reconstruction
- Polishing abrasive in some toothpaste formulations as a milder alternative to silica
Safety Information
Low acute toxicity — GRAS as a food additive (E341), with no LD50 reported below 1 g/kg. Bulk handling raises a respirable-dust concern; OSHA treats it as nuisance dust at 15 mg/m³ total / 5 mg/m³ respirable. Long-term inhalation in mining and processing can contribute to mild pneumoconiosis. Implantable medical-grade β-TCP must meet ASTM F1088 specifications for trace heavy metals. No fire, reactivity, or environmental hazard at typical concentrations.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.