Gold number is associated with:

Options

A. Only lyophobic colloids
B. Only lyophilic colloids
C. Both lyophobic and lyophilic colloids
D. None of these

Answer

To solve the question about the association of the gold number, we can follow these steps:

### Step 1: Understand the Concept of Gold Number
The gold number is a measure used in colloid chemistry that indicates the protective power of a colloid. It is defined as the minimum amount of a lyophilic colloid (in milligrams) that prevents the coagulation of a standard gold sol (10 ml) when a specific amount of an electrolyte (1 ml of 10% NaCl solution) is added.

**Hint:** Remember that the gold number is specifically related to the protective ability of colloids against coagulation.

### Step 2: Identify the Types of Colloids
Colloids can be classified into two main types:
- **Lyophilic colloids**: These are solvent-loving colloids that are stable and do not easily coagulate.
- **Lyophobic colloids**: These are solvent-hating colloids that are less stable and more prone to coagulation.

**Hint:** Consider the stability and behavior of colloids when exposed to electrolytes.

### Step 3: Analyze the Definition of Gold Number
According to the definition, the gold number specifically refers to the amount of lyophilic colloid required to prevent coagulation. This indicates that the gold number is directly associated with lyophilic colloids.

**Hint:** Focus on the definition and its implications regarding the types of colloids involved.

### Step 4: Evaluate the Options
Now, let's evaluate the options provided:
1. Only lyophobic colloids
2. Only lyophilic colloids
3. Both lyophobic and lyophilic colloids
4. None of these

From our understanding, the gold number is associated only with lyophilic colloids.

**Hint:** Compare the definitions and characteristics of lyophilic and lyophobic colloids to determine the correct association.

### Step 5: Conclusion
Based on the analysis, the correct answer is that the gold number is associated with **only lyophilic colloids**.

**Final Answer:** The correct option is **Option 2: Only lyophilic colloids.**