The gold number of gelatin is `0.01` . Calculate the amount of gelatin to be added to `1000mL` of a colloidal sol of gold to prevent its coagulation, before adding `1mL` of `10%NaCl` solution.

Explanation

To solve the problem, we need to determine the amount of gelatin required to prevent the coagulation of a colloidal sol of gold when adding a specified volume of NaCl solution. The gold number of gelatin is given as 0.01, which indicates the amount of gelatin needed to stabilize a certain volume of gold sol in the presence of NaCl.

### Step-by-Step Solution:

1. **Understand the Gold Number**:
The gold number of gelatin is 0.01 mg per 10 mL of gold sol to prevent coagulation when 1 mL of 10% NaCl solution is added.

2. **Determine the Total Volume of Gold Sol**:
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