Correct the following statement by changing the underlined part of the sentence.
Non-stoichiometric NaCl is `ul("pink")`.

Explanation

To correct the statement "Non-stoichiometric NaCl is pink," we need to understand the properties of non-stoichiometric NaCl and the reason behind its color.

### Step-by-Step Solution:

1. **Understanding Non-Stoichiometric NaCl**:
- Non-stoichiometric NaCl refers to a type of sodium chloride where the ratio of sodium ions (Na⁺) to chloride ions (Cl⁻) is not 1:1. This can occur when there is a deficiency of chloride ions or an excess of sodium ions in the crystal lattice.

2. **Formation of F-Centers**:
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