Calcium Citrate (Tetrahydrate)

Calcium citrate is the tricalcium salt of citric acid, supplied commercially as the tetrahydrate, C12H10Ca3O14·4H2O, formula weight 570.51. It carries 21.1% elemental calcium as the tetrahydrate, or 24.1% expressed on the anhydrous basis. Formulators reach for it in place of the carbonate when the finished product needs to disperse or suspend rather than sit as a dense insoluble load, or when the citrate anion is wanted for its buffering and sequestering behaviour. It is very slightly soluble in water (0.085 to 0.096 g per 100 mL at 18 to 23 °C) and insoluble in ethanol, so it is handled as a suspendable fine powder rather than a soluble salt. The grade Thovek supplies meets the JECFA/FCC criteria for INS 333(iii): assay not less than 97.5% after drying, loss on drying between 10.0% and 14.0% at 150 °C for four hours (the bound water of the tetrahydrate), fluorides not more than 30 mg/kg and lead not more than 2 mg/kg, with the oxalate, free acid and free alkali tests passing. USP and EP/BP monograph grades are available where the buyer's registration file calls for them. Because the water of crystallisation sits inside the loss-on-drying window, buyers should specify whether they are contracting on an as-is or anhydrous-basis assay. Material is offered as fine powder and as coarser granular grades for direct compression and sachet filling, milled to an agreed mesh. Every lot carries a Certificate of Analysis covering assay, elemental calcium, loss on drying, heavy metals, residual solvents where applicable and full microbiology, plus MSDS and allergen, GMO and origin declarations for the import file. Standard export packing is 25 kg lined sacks or fibre drums, palletised for container loading.