22-02-2013, 02:24 PM
DETERMINATION OF TIN IN STANNOUS CHLORIDE
Theory :
To obtain an uniform coating of metallic tin over the article to be
electroplated, the concentration of Sn+2 ions requires to be
maintained requiring periodic checking of the Sn+2 ions in the
bath. Tin is estimated by oxidizing a known volume of SnCl2 with
an excess of standard I2 solution which oxidizes Sn+2 ions to Sn+4
ions. The unreacted I2 is then back titrated with standard solution
of Na2S2O3 in presence of starch indicator. The amount of I2
consumed is equivalent to the amount of Tin in SnCl2 and the
strength of tin can be calculated.
Procedure :
I. Standardization of Na2S2O3 :
1. Pipette out 10 ml of 0.1 N K2Cr2O7 into stopper bottle and add
20 ml of 2N H2SO4 by a measuring cylinder.
2. Add 10ml of 10 % KI solution by pipette. Stopper the bottle,
mix the content and keep the bottle in dark for about 10 mins.
3. Dilute the contents by addition of 20 ml of tap water by
measuring cylinder and titrate against supplied Na2S2O3
solution till the red brown colour changes to straw yellow .
4. Add about 1 ml of starch indicator and continue the titration till
the blue colour formed changes to green.
5. Note the burette reading V ml and calculate the normality of
supplied Na2S2O3 solution.
Result : The amount of Tin in diluted solution of stannous chloride =
_____ gm / lit.
Theory :
To obtain an uniform coating of metallic tin over the article to be
electroplated, the concentration of Sn+2 ions requires to be
maintained requiring periodic checking of the Sn+2 ions in the
bath. Tin is estimated by oxidizing a known volume of SnCl2 with
an excess of standard I2 solution which oxidizes Sn+2 ions to Sn+4
ions. The unreacted I2 is then back titrated with standard solution
of Na2S2O3 in presence of starch indicator. The amount of I2
consumed is equivalent to the amount of Tin in SnCl2 and the
strength of tin can be calculated.
Procedure :
I. Standardization of Na2S2O3 :
1. Pipette out 10 ml of 0.1 N K2Cr2O7 into stopper bottle and add
20 ml of 2N H2SO4 by a measuring cylinder.
2. Add 10ml of 10 % KI solution by pipette. Stopper the bottle,
mix the content and keep the bottle in dark for about 10 mins.
3. Dilute the contents by addition of 20 ml of tap water by
measuring cylinder and titrate against supplied Na2S2O3
solution till the red brown colour changes to straw yellow .
4. Add about 1 ml of starch indicator and continue the titration till
the blue colour formed changes to green.
5. Note the burette reading V ml and calculate the normality of
supplied Na2S2O3 solution.
Result : The amount of Tin in diluted solution of stannous chloride =
_____ gm / lit.