Why is potassium chloride sometimes violet instead of pure white ?

Explanation

To understand why potassium chloride (KCl) can appear violet instead of pure white, we need to delve into the concept of color centers, specifically F-centers. Here’s a step-by-step explanation:

### Step 1: Understand the Color of Pure Potassium Chloride
Potassium chloride is typically a white crystalline solid. The white color is due to the way the crystal lattice structure interacts with light, reflecting and scattering it uniformly.

**Hint:** Think about how pure substances reflect light without any color interference.

### Step 2: Introduction to F-Centers
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