Here's how to find it:

1. Molecular Formula: The molecular formula for tartaric acid is C₄H₆O₆.

2. Simplify the Ratio: Find the greatest common factor (GCD) of the subscripts in the molecular formula. In this case, the GCD is 2.

3. Divide by GCD: Divide each subscript in the molecular formula by the GCD.

* C₄H₆O₆ / 2 = C₂H₃O₃

4. Empirical Formula: The simplified formula, C₂H₃O₃, can be further simplified to CH₂O₃.

Therefore, the empirical formula for tartaric acid is CH₂O₃.