For coagulation of 10ml of a positive sol, the volumes of IM each `NaCl, Na_(2),SO_(4),Na_(3)PO_(4) and Na_(4)[Fe(CN)_(6)]` required separately are P, Q, R and S ml respectively. Arrange P, Q, R and S in the descending order. 

Explanation

For coagulation of a positive sol, negative ions are required.
As per Hardy-Schulze rule greater the valence of the flocculating ions, greater is the flocculating power and lesser volume is required.
Thus the correct order of the volume of solutions is ` P gt Q gt R gt S` .