Name the law on which this principle is based.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Principle of Calorimetry**: The principle of calorimetry states that the heat lost by a hot body is equal to the heat gained by a cold body when they are in thermal contact, assuming no heat is lost to the surroundings.

2. **Identifying the Law**: This principle is fundamentally based on the law of conservation of energy. The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another.

3. **Conclusion**: Therefore, the law on which the principle of calorimetry is based is the **Law of Conservation of Energy**.

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