Dear Abdullah,

Herein the required equation:

MSI = [1-C1/C2] x 100

where C1 and C2 are electrical conductivity of the water containing samples  and 2.

For more details on this equation and topic of concern, please use the following link:

http://www.idosi.org/wjas/wjas3(2)/6.pdf

Hoping this will be helpful,

Rafik

Many thanks Dr. Rafik Karaman

That was too helpful