The experiment is determination of amount of Fe in vitamin tablets. It has to prepare the standard solution for construct calibration curves first, and to prepare the sample solution of Haemo-vit brand and FBC brand. The first step, standard preparation step, hydroquinone is added for generate Fe2+ and then to form color by adding o-phenanthroline. The second step is to prepare sample solution from tablet. Before adding hydroquinone and o phenanthroline, should boil the solution with 25 ml of 6 M HCl for prepare sample because it is inorganic compound. From the color of solution sample can predict the concentration, the sample solution is orange-red color, after add o-phenanthroline. Haemo-vit sample solution color is lighter than FBC sample, so Fe in FBC tablet should be greater than Heamo-vit tablet because o phenanthroline form with Fe2+ to formlFe (o-phen) 312+ in each sample. Finally, measuring the absorbance of the solution, the absorbance of standard solution is detected from the vis-spectrophotometer use to graph a calibration curve From the calibration curve of Fe standard solution, the linearity is 0.9997, R2 0.9997, lt means that the result is uncertainty because the good experiment result linearity should be equal one. Therefore, linearity is be 0.9997 then be an accept value of the result For the result of experiment, the amount of FBC sample tablet is 63.21 mg (In fact, FBC is contained Fe 200 mg), and the amount of Haemo-vit sample tablet is 33.36 mg (In fact Haemo-vit is contained Fe 135 mg). Therefore, the amount of Fe that detected is less than real. There are several processes; grind sample, wet digestion, dilution, for preparing the sample, so it may affect the value of amount of Fe is lost. In the same way, the company may label over the real it is possible