To calculate the empirical formula, enter the composition (e.g. C=40%, H=6.67%, O=53.3%) of the compound. Enter an optional molar mass to find the molecular formula. Percentages can be entered as decimals or percentages (i.e. 50% can be entered as .50 or 50%.) To determine the molecular formula, enter the appropriate value for the molar mass. Bismuth(III) Ions: Bismuth(III) forms a highly insoluble hydroxide which upon treatment with the hydroxy complex of tin(II) is immediately converted to free bismuth, a black precipitate. 3Sn(OH) 4 2-(aq) + 2Bi(OH) 3 (s) → 2Bi(s) + 3Sn(OH) 6 2-(aq) Precipitate Bi 3+ from the test solution with 3 M NaOH and centrifuge the precipitate. Then, to a solution of tin(II) chloride add with stirring 6 M sodium hydroxide until the precipitate of tin(II) hydroxide which first forms just redissolves.