JeremyBenson11
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I'm looking at two different articles for calculating total acidity, without any scientific background and a lack of math skills one is a bit harder. I was wondering the more scientific method is vastly different than the second method. The second method is the simplified NaOH method with and without pH meter. I assume the harder method is more accurate? I'll show both below.
First Method:
15 ml sample titrated out with 12.6 ml of the 0.1 molar solution of sodium hydroxide (NaOH).
1. Calculate molar mass of acid in sample as sum mass of all atoms in the melucule.
- The molar ass of Tartaric Acid:
(C4H6O6)=4 x M(C)+6 x M(H)+6 x M(O)=4 x 12+6 x 1+6 x 16=150 g/mole.
150 g/mole.
2. Caluclate number of moles of NaOh by multiplying volume of NaOH by its concentration.
Number of moles = Volume (in L) x molar (mole/L) concentration.
number of moles (NaOH) = 0.0126 L x 0.1 mole/L= 0.00126 moles.
0.00126 moles.
3. Divide moles of acid by sample volume and multiply by 100 to find acid amount in 100ml.
(C4H6O6) = 0.00063 moles x 100 ml/15 ml = 0.0042 moles.
0.0042 moles.
4. Multiply the acid amount in 100 ml (Step 5) by its molar mass (Step 1) to calculate titratable acidity (in g/100 ml).
titratable acidity = 0.0042 x 150 = 0.63 g/100 ml.
0.63 g/100 ml.
Second Method:
Calibrate the pH meter using a two point calibration. The most common buffer solutions used for calibration are pH 7 and pH 4 but pH 10 is also available. Our pH meter has two set screws with one marked pH 7 and the other pH 4 or 10. Fresh pH buffer solutions are important to assure accuracy in the calibration of the meter.
First, calibrate with pH 7 buffer because this is a weaker solution. If the meter does not read pH 7 with the pH 7 buffer, we turn set screw marked pH 7.0 to attain 7.0.
Then calibrate with the pH 4 buffer solution turning the set screw marked pH 4, or whatever method used for your meter.
Add a known amount of grape juice or wine into a beaker (usually 10 milliliters).
Place the pH meter into the solution. At this point you can take a reading of the pH of the must or wine.
Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) to the solution until the pH meter reads 8.2. In our set-up, we have a stand that supports a 10 ml burette with a stopcock on the bottom of the burette. The burette is calibrated in 0.1 increments. When the stopcock is opened, the solution is allowed to flow into the beaker. Closing the stopcock stops the flow of solution and allows a reading from the burette of how much solution has been dispensed. As the solution pH rises to around a pH of 6.0, changes occur faster so be careful as you pass pH 7.0 on your way to pH 8.2.
Use the following formula to determine the TA of your wine or must. TA = (Number or milliliters of NaOH / Number of milliliters of juice) X 0.75 The units for the TA in this calculation are: Number of grams of tartaric acid per 100 milliliters of juice.
First Method:
15 ml sample titrated out with 12.6 ml of the 0.1 molar solution of sodium hydroxide (NaOH).
1. Calculate molar mass of acid in sample as sum mass of all atoms in the melucule.
- The molar ass of Tartaric Acid:
(C4H6O6)=4 x M(C)+6 x M(H)+6 x M(O)=4 x 12+6 x 1+6 x 16=150 g/mole.
150 g/mole.
2. Caluclate number of moles of NaOh by multiplying volume of NaOH by its concentration.
Number of moles = Volume (in L) x molar (mole/L) concentration.
number of moles (NaOH) = 0.0126 L x 0.1 mole/L= 0.00126 moles.
0.00126 moles.
3. Divide moles of acid by sample volume and multiply by 100 to find acid amount in 100ml.
(C4H6O6) = 0.00063 moles x 100 ml/15 ml = 0.0042 moles.
0.0042 moles.
4. Multiply the acid amount in 100 ml (Step 5) by its molar mass (Step 1) to calculate titratable acidity (in g/100 ml).
titratable acidity = 0.0042 x 150 = 0.63 g/100 ml.
0.63 g/100 ml.
Second Method:
Calibrate the pH meter using a two point calibration. The most common buffer solutions used for calibration are pH 7 and pH 4 but pH 10 is also available. Our pH meter has two set screws with one marked pH 7 and the other pH 4 or 10. Fresh pH buffer solutions are important to assure accuracy in the calibration of the meter.
First, calibrate with pH 7 buffer because this is a weaker solution. If the meter does not read pH 7 with the pH 7 buffer, we turn set screw marked pH 7.0 to attain 7.0.
Then calibrate with the pH 4 buffer solution turning the set screw marked pH 4, or whatever method used for your meter.
Add a known amount of grape juice or wine into a beaker (usually 10 milliliters).
Place the pH meter into the solution. At this point you can take a reading of the pH of the must or wine.
Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) to the solution until the pH meter reads 8.2. In our set-up, we have a stand that supports a 10 ml burette with a stopcock on the bottom of the burette. The burette is calibrated in 0.1 increments. When the stopcock is opened, the solution is allowed to flow into the beaker. Closing the stopcock stops the flow of solution and allows a reading from the burette of how much solution has been dispensed. As the solution pH rises to around a pH of 6.0, changes occur faster so be careful as you pass pH 7.0 on your way to pH 8.2.
Use the following formula to determine the TA of your wine or must. TA = (Number or milliliters of NaOH / Number of milliliters of juice) X 0.75 The units for the TA in this calculation are: Number of grams of tartaric acid per 100 milliliters of juice.