The triple point of water is a standard fixed point in modern thermometry. Why ? Why melting point of ice or boiling point of water not used as standard fixed points.(as was originally done in celsius scale)

Explanation

### Step-by-Step Solution:

1. **Understanding the Triple Point of Water**:
The triple point of water is defined as the unique combination of temperature and pressure at which water can coexist in three phases: solid (ice), liquid (water), and gas (water vapor). For water, this occurs at a temperature of 273.16 K (0.01 °C) and a pressure of 4.58 mm of mercury.

2. **Significance of the Triple Point**:
The triple point is considered a standard fixed point in thermometry because it is a precise and reproducible condition. This means that under the same temperature and pressure, all substances will exhibit the same properties, making it a reliable reference point for calibrating thermometers.

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