Introduction

The Acid Balancing panel calculates the amount of acid to add to a given must or wine to raise the acidity to a specified level.  It can also estimate the amount of Calcium Carbonate, Potassium Carbonate, or Potassium Bicarbonate required to reduce the acidity to a target level.

Making a Calculation

To make a calculation, follow these steps:

1. Select Calculation > Acid Balancing from the menu, or select the Acid tab at the top of the main window.
2. Select the appropriate units for the input fields using the drop-down menus in the right-hand column.
3. Enter the Wine Volume, Initial Acidity, and Target Acidity in the appropriate fields.
4. If the target acidity is greater than the initial acidity, FermCalc will show a dropdown list of acid types for increasing the acidity. Select the Acid Type from the drop-down menu.
5. If the target acidity is less than the initial acidity, FermCalc will show a dropdown list of additives for reducing the acidity. Select the Additive Type from the drop-down menu.

The calculated amount of acid or additive required to achieve the target acidity will appear in the Additive Required field.

Calculation Details

There are two scenarios we need to consider for this calculation.

1. Initial acidity is less than the target acidity .
2. Initial acidity is greater than the target acidity .

Case 1: Initial Acidity is Less Than the Target Acidity

For this case we'll be adding acid to increase the acidity. FermCalc first converts the target acidity to the % Tartaric reference using the conversion factors explained in the Acidity Conversions discussion.

By definition, the amount of Tartaric Acid required to raise acidity by 1% Tartaric is simply 0.01 kilograms/liter. To calculate the required addition of the selected acid to yield the target acidity in the % Tartaric reference, we need to know its molecular weight and the number of H⁺ ions it yields in solution. These parameters are listed in the table below.

Acid	Molecular Weight	H+ Ions
Tartaric	150.09	2
Malic	134.09	2
Citric	210.14	3

Knowing the values, the equation to calculate the amount of acid to add is

ma = 0.01v(it/ia)(mwa/mwt)(at - ai)

(1)

where

m_a = mass of acid required (kg)
v = volume of wine (liters)
i_t = number of H⁺ ions per molecule for Tartaric Acid
i_a = number of H⁺ ions per molecule for the acid being added
mw_t = molecular weight of Tartaric Acid
mw_a = molecular weight of the acid being added
a_t = target acidity, % Tartaric
a_i = initial acidity, % Tartaric

For Acid Blend, the composition is assumed to be 40% Tartaric, 40% Malic, and 20% Citric acids.

Case 2: Initial Acidity is Greater Than the Target Acidity

For this case we'll need to add either Calcium Carbonate (CaCO₃), Potassium Carbonate (K₂CO₃), or Potassium Bicarbonate (KHCO₃) to reduce the acidity. All three of these work by neutralizing Tartaric acid, or H₂T, where T represents a Tartrate ion. The reactions are:

CaCO3 + H2T  --->  CaT + H2O + CO2	(2)
K2CO3 + 2H2T  --->  2KHT + H2O + CO2	(3)
KHCO3 + H2T  --->  KHT + H2O + CO2	(4)

To calculate the required amount of any of these additives, we need to know their molecular weights as well as the number of H₂T molecules that are neutralized by each molecule of additive. These parameters are tabulated below.

Additive	Molecular Weight	Molecules of H2T Neutralized
Calcium Carbonate	100.09	1
Potassium Carbonate	138.21	2
Potassium Bicarbonate	100.12	1

The following equation is used to calculated the required amount of additive.

mr = 0.01v[mwr/(n·mwt)](ai - at)

(5)

where

m_r = mass of acidity reducer required (kg)
v = volume of wine (liters)
mw_t = molecular weight of Tartaric Acid
mw_r = molecular weight of the acidity reducer being added
n = molecules of H₂T neutralized
a_t = target acidity, % Tartaric
a_i = initial acidity, % Tartaric

For additional information on using these additives, see this article by Bill Collings.