Volumetric Determination of Tin II Chloride

In this direct titration, iodine oxidises Sn(II) to Sn(IV) and the extra drop of iodine is detected by starch indicator. 

Weigh out accurately about 2.0 g of purest tin(II) chloride into a beaker, add 150 cm cone. HCl and shake to dissolve. Transfer quantitatively to a 250 cm volumetric flask and make up to the mark using boiled-out distilled water. Pipette 25.0 cm of die solution to a 250 cm Buchner flask, add 75 cm boiled-out water and 2 cm fireshly prepared starch solution. Insert the tip of a burette containing 0.05 M iodine solution into the bung of the flask. Apply gentle suction and titrate with the iodine solution to the first appearance of a blue colour. Repeat to obtain concordant results and calculate from the average titre the concentration of Sn(II) in mol dm.  

---