What is the significance of reciprocal of "gold number"?

Explanation

To understand the significance of the reciprocal of the "gold number," we can break it down into clear steps:

### Step-by-Step Solution:

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

2. **Understanding Coagulation**:
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