Purity Calculation of Na2S2O5

[blackcool]

Hi to all great member,

This is my first post on this forum after joining a few days ago. Nice meeting all of science people here....

 

I am really need clarification on how to calculate the purity of Sodium Meta Bisulfite above. I do the titration with Iodine 0.1 N until the color changes to faint black with starch indicator.

 

In water the Na2S2O5 + H2O ---> 2NaHSO3.

 

The purity calculated as:

{(VxNx47.5) / W mg)} x 100% = % w/w Na2S2O5 as Na2S2O5.

 

Is the above equation correct?. Any other thought?

 

Google was no help anyway .

 

Thankyou in advance.

[blackcool]

Please someone help... .

[YT2095]

check the references at the bottom of this page: http://www.mun.ca/educ/ed4361/virtual_academy/campus_a/woodlandm/Demo1.html