# Acid Titration Calculator

### Indroduction

The Acid Titration Calculator determines the titratable acidity (TA) of a wine sample given the volume of the sample and the volume of sodium hydroxide (NaOH) added during a titration test.

### Input Field Definitions

Wine Sample Volume – The volume of the wine sample being titrated.

Volume of NaOH Added – The volume of NaOH solution required to reach the titration endpoint.

NaOH Normality – The normality (moles/liter) of the NaOH solution used to titrate the wine sample.

### Output Field Definitions

Titratable Acidity (TA) – The calculated titratable acidity of the wine sample.

### Calculation Details

Acid titration makes use of the neutralization reaction between NaOH and the acids present in wine. In this reaction, the OH ions contributed by the NaOH and the H+ ions contributed by the wine acids combine to form water, H2O. The reaction is complete when all of the H+ ions have been neutralized by OH ions.  Since each OH ion neutralizes one H+ ion, we can write a balance between the H+ and OH ions as:

 ia(ma/mwa) = vnNn (3-1)

where:

ia = number of H+ ions donated by each molecule of acid

mwa = molecular weight of acid, grams/mole

ma = mass of acid, grams

vn = volume of NaOH added, liters

Nn = normality of NaOH solution, moles/liter

The mass of the acid in solution is simply the acidity multiplied by the volume or:

 ma = a·vw (3-2)

where:

a = acidity, grams/liter

vw = volume of wine sample, liters

Combining equations (3-1) and (3-2) and solving for acidity we get:

 a = (mwa/ia)vnNn / vw (3-3)

By titrating for acidity, all we’ve really determined is the number of available H+ ions in the solution and not the types of acid present.  For this reason we must choose an acid as a reference in order to express the acidity as a concentration. Tartaric acid is frequently used as a reference, and is the default acid reference in FermCalc. For tartaric acid, mwa is 150.09, and ia is equal to 2, so equation (3-3) becomes:

 a = 75.045·vnNn / vw (3-4)