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 can follow these steps:

### Step 1: Understand the Definition of Gold Number
The gold number is defined as the minimum amount of protective colloid (in milligrams) required to prevent the coagulation of 10 mL of a gold solution when 1 mL of a 10% NaCl solution is added.

### Step 2: Convert the Mass of Colloid to Milligrams
We are given that 0.25 g of the lyophilic colloid is added. We need to convert this mass into milligrams:
\[ 0.25 \, \text{g} = 0.25 \times 1000 \, \text{mg} = 250 \, \text{mg} \]

### Step 3: Calculate the Amount of Colloid per mL of Gold Solution
Since the colloid is added to 100 mL of gold solution, we need to find out how much colloid is present in 1 mL of the solution:
\[ \text{Amount of colloid in 1 mL} = \frac{250 \, \text{mg}}{100 \, \text{mL}} = 2.5 \, \text{mg/mL} \]

### Step 4: Determine the Amount of Colloid Required for 10 mL of Gold Solution
To find the amount of colloid needed to prevent coagulation in 10 mL of gold solution, we multiply the amount of colloid in 1 mL by 10:
\[ \text{Amount of colloid for 10 mL} = 2.5 \, \text{mg/mL} \times 10 \, \text{mL} = 25 \, \text{mg} \]

### Step 5: Conclusion
The gold number of the lyophilic colloid is therefore 25 mg.

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

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