By Contributing Writer
Updated Mar 24, 2022

Accurate titratable acidity measurement is essential for winemakers, quality control labs, and food technologists. It quantifies the total amount of acids in a solution by titrating with a standard sodium hydroxide (NaOH) solution, using a pH‑sensitive indicator to pinpoint the endpoint. The result, expressed in grams per 100 mL, is a key parameter in wine evaluation, especially where tartaric acid dominates.

Below is a clear, industry‑standard method to determine titratable acidity, illustrated with a tartaric acid example.

Step 1: Determine the Acid’s Molar Mass

Calculate the molar mass by summing the atomic weights of all constituent atoms. For tartaric acid (C₄H₆O₆), use the periodic table values:
M(C)=12, M(H)=1, M(O)=16.

Molar mass = 4×12 + 6×1 + 6×16 = 150 g mol^–1.

Step 2: Compute Moles of NaOH Used

Multiply the titrant volume by its molarity:

Volume of NaOH = 12.6 mL = 0.0126 L
Concentration = 0.1 mol L^–1

Moles NaOH = 0.0126 L × 0.1 mol L^–1 = 0.00126 mol.

Step 3: Write the Neutralization Reaction

C₄H₆O₆ + 2 NaOH → C₄H₄O₆Na₂ + 2 H₂O

Step 4: Calculate Moles of Acid

One mole of tartaric acid reacts with two moles of NaOH. Therefore:

Moles acid = 0.00126 mol NaOH ÷ 2 = 0.00063 mol.

Step 5: Scale to 100 mL

Adjust for the aliquot volume (15 mL):

Acid in 100 mL = 0.00063 mol × (100 mL ÷ 15 mL) = 0.0042 mol.

Step 6: Convert to g / 100 mL

Multiply by the molar mass:

Titratable acidity = 0.0042 mol × 150 g mol^–1 = 0.63 g / 100 mL.

What You’ll Need

• Scientific calculator
• Periodic table of elements (e.g., RSC Periodic Table)