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Note that bottles of NaOH should be capped so as to avoid as much exposure to the air as possible. This is because NaOH reacts with CO<sub>2</sub> in the air, causing the NaOH to become inaccurate as a base titration overtime <ref>[https://www.sciencedirect.com/science/article/pii/S2405656116300578 A novel rate of the reaction between NaOH with CO<sub>2</sub> at low temperature in spray dryer. Yadollah Tavan, Seyyed Hossein Hosseini. 2017. DOI: https://doi.org/10.1016/j.petlm.2016.11.006.]</ref><ref>[https://www.chem.indiana.edu/wp-content/uploads/2017/11/17-3-Sodium-Hydroxide-and-Carbon-Dioxide.doc "Sodium Hydroxide and Carbon Dioxide: Why it is Important to Keep Your Standard NaOH Solutions Capped". Indiana University course material. Retrieved 10/18/2018.]</ref><ref>[https://www.homebrewersassociation.org/how-to-brew/resources/conference-seminars Robert Hall. The "Sour" in Sour Beers: Microbiology Sensory Perception and Styles. HomebrewCon 2018 Seminar. 2018.]</ref> (~42:00 mins in).
The [https://docs.google.com/spreadsheets/d/1DR48ivi9xSoKOl3TmsaqhWg8yLlcP6BgO5eKZ-suITo/edit?usp=sharing Eccentric Beekeeper TA Spreadsheet] (save a copy to your local computer to use it) calculates TA as well as blends of beers with different TA values. It also includes a correction for beer final gravity. The idea is that the more residual sugar there is the less effect the acid will have on your perception. This is likely not that straightforward since you can have varying levels of sweetness at the same given FG <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1097532690274944/?comment_id=1097668506928029&offset=0&total_comments=19&comment_tracking=%7B%22tn%22%3A%22R5%22%7D Conversation with Dave Janssen on MTF. 6/23/2015.]</ref>.
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Why care about titratable acidity? pH quantifies the number of free hydrogen ions (or hydrogen ion equivalents) in liquid. Your palate does not measure pH directly. Your palate interprets a multi-variable substrate called beer, which also contains "weak acids" such as lactic acid that contain bonded hydrogen ions that are not measured by pH. Titratable acidity attempts to put another quantifiable handle on your beer akin to pH; the measurement better captures how “acidic” the beer may taste to you. Again, there are other acids than lactic in the beer, leading to differences in flavor between beers of the same TA. As a general rule of thumb, the lower the pH, the higher the TA, however, TA and pH are not directly correlated. TA has been proposed as a more accurate representation of perceived acidity because we taste both free hydrogen ions and those that are bound to organic acids <ref>[http://www.craftbrewersconference.com/wp-content/uploads/2015_presentations/W1320_Kara_Taylor.pdf Kara Taylor. CBC 2015 Presentation. 2015. Retrieved 11/14/2017.]</ref><ref>[http://www.cider.org.uk/phandacid.htm The Wittenham Hill Cider Portal. "Relationship between pH and Titratable acid in Cider Apple Juices". Retrieved 11/14/2017.]</ref>. There is some disagreement on whether TA is a more accurate measurement of perceived acidity than pH; see [[Titratable_Acidity#Limitations_of_TA|Limitations of TA]] for details.
Titratable acidity can be expressed in terms of different acids. In wine, TA is generally expressed in terms of tartaric acid (molecular weight of 150.09). In sour beer, TA is expressed in terms of lactic acid (molecular weight 90.08, which is where the "0.9" number comes from in the equation below). To express TA in terms of a specific acid, the molecular weight of the specified acid is used in the TA calculation. In the [[Titratable_Acidity#Example|example below]], we express the TA value in terms of lactic acid. See [http://www.awri.com.au/wp-content/uploads//TN14.pdf appendix 1 in this paper] on how to convert the titratable acidity value for different acids. Note that this is NOT a measurement of how much lactic acid or tartaric acid there is, it is an expression of measurement like how feet and meters are two different expressions of measurement for the same thing (distance). For example, a TA of 35.0 measured in units of tartaric acid is equal to a TA 36.6009 0015 measured in units of lactic acid. Therefore, an argument can be made that TA measurements should always be specified as to which acid was used in the calculation.
The ASBC<ref name="ASBC" /> equation for TA in units of lactic acid (the 0.9 constant represents TA expressed in units of lactic acid) is as follows:
[[File:TA Formula.gif|center|Titratable Acidity Example]]
===Example===
* Sodium Hydroxide, NaOH. Available in liquid or powder form. Be sure to note its molarity (M), units of mol/L. For more info on mol, see [https://en.wikipedia.org/wiki/Mole_(unit) here].
:*<code>'''Safety caution''': always wear safety glasses and gloves when handling NaOH in any concentration. NaOH can cause severe burns. In concentrations higher than 0.1, NaOH can corrode through clothing. See [https://www.ccohs.ca/oshanswers/chemicals/chem_profiles/sodium_hydroxide.html Canadian Centre for Occupational Health and Safety on Sodium Hydroxide].</code> :*Note that bottles of NaOH should be capped so as to avoid as much exposure to the air as possible. This is because NaOH reacts with CO<sub>2</sub> in the air, causing the NaOH to become inaccurate over time as a base titration <ref>[https://www.sciencedirect.com/science/article/pii/S2405656116300578 A novel rate of the reaction between NaOH with CO<sub>2</sub> at low temperature in spray dryer. Yadollah Tavan, Seyyed Hossein Hosseini. 2017. DOI: https://doi.org/10.1016/j.petlm.2016.11.006.]</ref><ref>[https://www.chem.indiana.edu/wp-content/uploads/2017/11/17-3-Sodium-Hydroxide-and-Carbon-Dioxide.doc "Sodium Hydroxide and Carbon Dioxide: Why it is Important to Keep Your Standard NaOH Solutions Capped". Indiana University course material. Retrieved 10/18/2018.]</ref><ref>[https://www.homebrewersassociation.org/how-to-brew/resources/conference-seminars Robert Hall. The "Sour" in Sour Beers: Microbiology Sensory Perception and Styles. HomebrewCon 2018 Seminar. 2018.]</ref> (~42:00 mins in).
* Nitrile or latex gloves. NaOH is a strong base, it will hurt you if you get any on your skin.
At or around a pH of 8.2, we have reached our equivalence point for a titration of pure NaOH and pure lactic acid. We need to convert the moles of NaOH we added into moles of lactic acid, and then divide the equivalent grams of lactic acid by the original volume of beer. That gets us g/L, and our titratable acidity. For a numerical example, assume '''15mL''' beer with a gravity of '''1.015''', '''5mL''' 0.1M NaOH:
[[File:TA example.gif|center|Titratable Acidity Example]]
In summary, the measurement of titratable acidity is a technique to quantify the total acid level of a beer. A major assumption was made: all the acid in the liquid was lactic acid. Two beers could have the same TA measurement, but have differing levels of palatable acidity, due to the acid makeup of the beer.
===Eccentric Beekeeper TA Calculator===
The [https://docs.google.com/spreadsheets/d/1DR48ivi9xSoKOl3TmsaqhWg8yLlcP6BgO5eKZ-suITo/edit?usp=sharing Eccentric Beekeeper TA Spreadsheet] (save a copy to your local computer to use it) calculates TA as well as blends of beers with different TA values. It also includes a correction for beer final gravity. The idea is that the more residual sugar there is the less effect the acid will have on your perception. This is likely not that straightforward since you can have varying levels of sweetness at the same given FG <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1097532690274944/?comment_id=1097668506928029&offset=0&total_comments=19&comment_tracking=%7B%22tn%22%3A%22R5%22%7D Conversation with Dave Janssen on MTF. 6/23/2015.]</ref>.
===ASBC Modification Using Mass===