Ascorbic acid $($vitamin C$)$ content in soluble vitamin C tablets was studied using iodometric titration. For the sample solution, $1$ soluble vitamin tablet with a mass of $4\mathrm{.}0088$ g was taken for analysis, dissolved in water and transferred to a $100$ mL volumetric flask. $10$ mL of $0\mathrm{.}1$ M HCl solution was added to the sample and the flask was then filled to the mark with deionized water and mixed carefully.

To prepare a solution for titration, $10$ mL KIO$3$ solution with concentration of $2\mathrm{.}370$ mmol$/$L$,5$ mL of $10\%$ KI solution and $25$ mL $0\mathrm{.}1$ M HCl solution were added to an Erlenmeyer flask to create a free iodine containing solution according to this reaction:

KIO$3+5$KI $+6$HCl $->3$I$2+6$KCl $+3$H$2$O

$10$ mL sample solution, prepared as described above, was then added to the same flask. Part of iodine reacted with ascorbic acid $($C$6$H$8$O$6)$ from the sample as follows:

I$2+$ C$6$H$8$O$6->$ C$6$H$6$O$6+2$HI

Part of iodine remained unreacted and was titrated with Na$2$S$2$O$3$ solution with concentration of $3\mathrm{.}48$ mmol$/$L:

I$2+2$Na$2$S$2$O$3->$ Na$2$S$4$O$6+2$NaI

The average titrant volume used over four replicate titrations was $11\mathrm{.}57$ mL with a standard deviation of $0\mathrm{.}0042$ mL$.$