0 . 25 g lyophillic colloid is added to 100 ml gold solution to prevent the coagulation on adding 1 ml 10% NaCl Solution . What will be gold number of tyophilic colloid ?

Options

A. 250
B. 125
C. 25
D. `0.25`

Answer

To find the gold number of the lyophilic colloid, we will follow these steps:

### Step 1: Convert the mass of the lyophilic colloid to milligrams
Given that 0.25 g of lyophilic colloid is added, we need to convert this to milligrams:
\[ 0.25 \text{ g} = 0.25 \times 1000 \text{ mg} = 250 \text{ mg} \]

### Step 2: Determine the amount of lyophilic colloid required to prevent coagulation in 10 ml of gold solution
The problem states that 250 mg of lyophilic colloid is added to 100 ml of gold solution. To find out how much is needed for 10 ml, we set up a proportion:
\[ \text{Amount for 10 ml} = \frac{250 \text{ mg}}{100 \text{ ml}} \times 10 \text{ ml} = 25 \text{ mg} \]

### Step 3: Identify the gold number
The gold number is defined as the amount of lyophilic colloid (in milligrams) that is required to prevent the coagulation of 10 ml of a standard gold solution when 1 ml of a 10% NaCl solution is added. From our calculation in Step 2, we found that 25 mg of the lyophilic colloid is needed to prevent coagulation in 10 ml of gold solution.

Thus, the gold number of the lyophilic colloid is:
\[ \text{Gold number} = 25 \text{ mg} \]

### Final Answer
The gold number of the lyophilic colloid is **25**.

---