on addition of 1 ml solution of `10% NaCl` to 10 ml gold sol in the presence of 0.25g of strach, the coagulation is just prevented. Strach has the following gold number

Options

A. 25
B. 0.025
C. 0.25
D. 2.5

Explanation

To determine the gold number of starch based on the given information, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Gold Number**:
The gold number is defined as the amount of a protective colloid (in this case, starch) in milligrams that is required to prevent the coagulation of 10 ml of a standard gold sol when a specific amount of an electrolyte (1 ml of 10% NaCl solution) is added.

2. **Identifying Given Values**:
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