coagultion is the process by which the dispersed phase of a colloid is made to aggregate and thereby separtate from the continuous phase. The minimum concetration of an eletrolyte in milli-moles per litre of the electrolyte solution which required to cause the caogultion of colloidal sol is called coagution value .
therefroe higher is the coagulatings power of effective ion, smaller will be the coagultion value of the electrolyte.
the ability of an ion to bring about coagulation of a given colloid depends upon :

Options

A. the sign of its charge
B. magnitude of its charge
C. both magnitude and sigh
D. none of these

Answer

To solve the question regarding the factors that influence the ability of an ion to cause coagulation of a colloidal sol, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Coagulation**:
Coagulation is the process where the dispersed phase of a colloid aggregates and separates from the continuous phase. This is essential to understand as it sets the context for the factors affecting coagulation.

**Hint**: Remember that coagulation involves the aggregation of particles in a colloid, leading to separation from the medium.

2. **Coagulation Value**:
The coagulation value is defined as the minimum concentration of an electrolyte (in millimoles per liter) required to cause coagulation of a colloidal sol. A lower coagulation value indicates a stronger coagulating power of the electrolyte.

**Hint**: Focus on the relationship between coagulation value and the effectiveness of electrolytes in causing coagulation.

3. **Factors Affecting Coagulation**:
The ability of an ion to cause coagulation depends on:
- **Charge of the Ion**: The charge of the ion plays a crucial role. For example, if the dispersed phase is negatively charged, a positively charged ion is required for coagulation.
- **Magnitude of the Charge**: The strength of the charge (magnitude) also matters. A higher charge leads to stronger electrostatic attractions, enhancing the coagulation process.

**Hint**: Consider how both the type (positive or negative) and the strength of the charge influence the coagulation process.

4. **Conclusion**:
Therefore, the ability of an ion to bring about coagulation of a given colloid depends on both the magnitude and the sign of the charge of the ion. This means that both the type of charge (positive or negative) and the strength of that charge are important for effective coagulation.

**Hint**: Remember that both aspects (magnitude and sign) are crucial for understanding the coagulation process.

### Final Answer:
The ability of an ion to bring about coagulation of a given colloid depends upon both the magnitude and sign of the charge of the ion.