Stannous Fluoride

Tin (II) fluoride SnF2, commercially referred to commercially as stannous fluoride. It is a colorless solid used as an ingredient in toothpastes that are typically more expensive than those that use sodium fluoride. Stannous fluoride converts the calcium mineral apatite into fluorapatite, which makes tooth enamel more resistant to bacteria-generated acid attacks. In toothpastes containing calcium minerals, sodium fluoride becomes ineffective over time, while stannous fluoride remains effective in strengthening tooth enamel. SnF2 acts as a Lewis acid.SnF2 is a reducing agent.

Stannous Fluoride USP GradeSnF2 -- 156.71Tin fluoride (SnF2) [7783-47-3].Stannous Fluoride contains not less than 71.2 percent of stannous tin (Sn ++), and not less than 22.3 percent and not more than 25.5 percent of fluoride (F), calculated on the dried basis.

Identification

pH: between 2.8 and 3.5, in a freshly prepared 0.4% solution.

Loss on drying: Dry it at 105C for 4 hours: it loses not more than 0.5% of its weight.

Water-insoluble substances: Transfer about 10 g, accurately weighed, to a 400-mL plastic beaker, add 200 mL of water, and stir with a plastic rod for 3 minutes, or until no more solid dissolves. Filter through a tared filtering crucible, and wash thoroughly, first with ammonium fluoride solution (1 in 100), then with water. [NOTEPrepare and use the filtering crucible in a well-ventilated hood.] Dry the residue at 105C for 4 hours, cool, and weigh: the weight of the residue does not exceed 0.2%.