Question

What is the formula to find the flocculation value?

Answer 1

Flocculation value:

• The flocculation value is the minimum concentration of an electrolyte that is required to cause coagulation or flocculation of a sol.
• It is expressed in terms of millimoles per liter ($\mathrm{mmol}/\mathrm{L}$).

The calculation for flocculation value:

Step 1: Take the example of coagulation of Sodium chloride in Arsenious sulfide sol

• Let $2\mathrm{mL}$ of $1\mathrm{M}$ $\mathrm{NaCl}$ coagulates $500\mathrm{mL}$ of Arsenious sulfide (${\mathrm{As}}_2{\mathrm{S}}_3$) sol.
• We can calculate the flocculating value for a sol as,

$2\mathrm{mL}$of $1\mathrm{M}\mathrm{NaCl}$ contains $\frac{2}{1000}$$\mathrm{mol}$ $=$$2\mathrm{millimole}$

• Therefore,$500\mathrm{mL}$ Arsenious sulfide sol requires$2\mathrm{millimoles}$$\mathrm{NaCl}$.

Step 2: Flocculation value of $\mathrm{NaCl}$

• $1000\mathrm{mL}$of Arsenious sulfide sol requires $4\mathrm{millimoles}$ of $\mathrm{NaCl}$.
• Flocculation value of $\mathrm{NaCl}$ is$4$.

Hence, the Flocculation value of $\mathrm{NaCl}$ is$4$.