A beginners guide to adding Pickling Lime to water to raise its "effective" alkalinity

[Silver_Is_Money]

Note: Calcium Hydroxide is also known as Pickling Lime and as Slaked Lime and Ca(OH)2

Note 2: There is no carbonate species component present within Ca(OH)2, so (since alkalinity is the measure of CaCO3), only an "effective" caustic equivalent to alkalinity can be achieved via its use.

For our example, let's assume the following:
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Our desired final target for mash water alkalinity = 100 ppm (or 100 mg/L)
Our initial mash water alkalinity = 30 ppm
Our volume of mash water to be raised to 100 ppm alkalinity = 5 gallons

Molecular Weight of Calcium Hydroxide = 74
Normality of Calcium Hydroxide = 2
Equivalent (or Normal) weight of Calcium Hydroxide = 74/2 = 37
Molecular weight of CaCO3 = 100
Normality of CaCO3 = 2
Equivalent (or Normal) weight of CaCO3 = 100/2 = 50
Molecular weight of calcium = 40
ppm = mg/L
1 Gal. = 3.7854 L


Procedure:
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Step 1) 100 ppm final alkalinity - 30 ppm initial alkalinity = 70 ppm of alkalinity "equivalent" to be added

Step 2) 5 Gal. mash water x 3.7854 Gal./L = 18.927 Liters of mash water to be treated

Step 3) 70 ppm x 37/50 x 18.927 L / 1,000 = 0.98 grams (rounded)

Our answer = Add 0.98 grams of calcium hydroxide to achieve an "effective" (or the caustic equivalent effect of) 100 ppm of alkalinity


Bonus stuff below this line:
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What is the resulting (additional) ppm of calcium?

(0.98 g x 1000) x 40/74 / 18.927 L = 28 mg/L (ppm) Ca++ [additional to source water ppm calcium]

 

[ajdelange]

The alkalinity of lime (at any normal brewing pH) is 2 mEq/mmol. No "effective" about it. That is the alkalinity. If you wish to follow north American practice you can multiply the 2 by 50 and express the alkalinity of lime as 100 ppm as calcium carbonate per mmol but again this is not an effective alkalinity. It is the alkalinity. As CaCO3 is not a good way to express alkalinity as it confuses many and makes calculation a little more difficult. Just remember that when you see alkalinity expressed as CaCO3 you should divide that number by 50 (not half the molecular weight of calcium carbonate which is slightly different from 50) to get a workable unit of alkalinity, milliequivalents.

 

[Silver_Is_Money]

The alkalinity of lime (at any normal brewing pH) is 2 mEq/mmol. No "effective" about it. That is the alkalinity. If you wish to follow north American practice you can multiply the 2 by 50 and express the alkalinity of lime as 100 ppm as calcium carbonate per mmol but again this is not an effective alkalinity. It is the alkalinity. As CaCO3 is not a good way to express alkalinity as it confuses many and makes calculation a little more difficult. Just remember that when you see alkalinity expressed as CaCO3 you should divide that number by 50 (not half the molecular weight of calcium carbonate which is slightly different from 50) to get a workable unit of alkalinity, milliequivalents.

A.J., thanks for correcting me on that. I don't believe that this correction in terminology changes the calculations as seen above, but if it does please let me know so I can make corrections.

 

[ajdelange]

Keep in mind what alkalinity is: the amount of acid required per unit of sample to lower the pH to a specified end point. Given that little wonder that people get confused when it is expressed as an amount of base (Calcium Carbonate) or the even more bizarre bicarbonate (Brun water is, AFAIK, the only place you'll see this).

For a strong base like lime or sodium hydroxide the amount of acid required to get to pH 4.3 or 4.4 or 4.5 is the same so alkalinity doesn't depend on the end point pH. For bases derived from weak acids, in particular carbonates and bicarbonates, it does so the end point pH must be specified.

 

[Silver_Is_Money]

Keep in mind what alkalinity is: the amount of acid required per unit of sample to lower the pH to a specified end point. Given that little wonder that people get confused when it is expressed as an amount of base (Calcium Carbonate) or the even more bizarre bicarbonate (Brun water is, AFAIK, the only place you'll see this).

Water in nature does not inherently or necessarily have grist added to it, and its alkalinity is derived outside of any reference to brewing. How far off is my simplified method for adding alkalinity? Is it over-stating waters alkalinity (or understating) by some nominal multiplicative factor?

 

[ajdelange]

Alkalinity is the same for potable water, grist, sodium bicarbonate, lye or vandium oxalate - the amount of acid required to move the pH from the intrinsic pH of the material to a specified reference pH. Understand this and you will be able to answer your own question. That's why I keep pushing people to understand the fundamental chemistry.

 

[Silver_Is_Money]

Alkalinity is the same for potable water, grist, sodium bicarbonate, lye or vandium oxalate - the amount of acid required to move the pH from the intrinsic pH of the material to a specified reference pH. Understand this and you will be able to answer your own question. That's why I keep pushing people to understand the fundamental chemistry.

A.J., my conclusion as seen in the first post to this thread is that to move 5 gallons of a typical 30 ppm alkalinity water to a state of 100 ppm alkalinity requires the nominal addition of 0.98 grams of Ca(OH)2. If you were personally going to move 5 gallons of a typical 30 ppm alkalinity water to 100 ppm of alkalinity via the addition of Ca(OH)2, how much Ca(OH)2 would you add to the 5 gallons of water? All others are encouraged to offer their own personal solution and answer (resulting quantity of Ca(OH)2 to be added) to this question here as well. I would much prefer answers to adversity. And I presume so would most others who are taking an interest in this thread.

Perhaps for the sake of the average Joe, I should preface this with a sitz im leben scenario in which we are in an era before computers and software, and we have just read in a book of a particular robust stout recipe that per the author requires mashing in 5 gallons of a nominal ballpark 100 ppm alkalinity water. The author has done this and knows from real world experience that this combination typically mashes at roughly 5.4 pH. And he therefore requests that you similarly mash in 100 ppm alkalinity water when using his recipe. And then he simply moves on to another topic and leaves us hanging. What should the average Joe (I perhaps in error called this average Joe a beginner at the onset, when not chemistry or heavy mathematics savvy should have been more appropriate) do at this juncture, given that all he knows is that his local water authority says his tap water has 30 ppm alkalinity?

 

[ajdelange]

I would much prefer answers to adversity.

This sort of implies that my suggestion that you understand the chemistry to the point that you can answer the question yourself is stirring up adversity. WTF? This is the Brewing Science forum where we hope to, among other things, to help people get to the point where they understand the science at least well enough to know that the answer to this question depends on the source water pH and the treated water's pH and the end point pH's that define the alkalinities. If we assume that the pHe's are the same and the treated water pH is to be the same as the starting water pH we realize that we need to absorb (100 - 30)/50 = 1.4 mEq/L more protons and that as Ca(OH)2 is a strong base (relative to potable water pH) with two (OH)'s we would thus require 0.7 mmol of Ca(OH)2/L. So that's my answer. There is no need to poll others as anyone who understands the chemistry will get that same answer under the same assumptions.

 

[Silver_Is_Money]

74 mg/L = 1 mmole
74 mg/L x 0.7 = 51.8 mg/L
51.8 mg/L x 18.927 L = 980 mg
980 mg = 0.98 g

The very same answer as I derived. Thank you kindly A.J.!

 

[Big Monk]

74 mg/L = 1 mmole
74 mg/L x 0.7 = 51.8 mg/L
51.8 mg/L x 18.927 L = 980 mg
980 mg = 0.98 g

The very same answer as I derived. Thank you kindly A.J.!

Again, you are not factoring in the pH dependency here. Yes, your answer matches with A.J. because he made the same assumptions as you.

Just like in your baking soda thread, normality will change with pH.

I can’t access the brewing functions right now but I believe what I said above is true. I’m always willing to stand corrected.

 

[Silver_Is_Money]

Again, you are not factoring in the pH dependency here. Yes, your answer matches with A.J. because he made the same assumptions as you.

Just like in your baking soda thread, normality will change with pH.

I can’t access the brewing functions right now but I believe what I said above is true. I’m always willing to stand corrected.

RPIScotty, Ca(OH)2 is a very strong base by comparison to the rather weak base that is commonly called Baking Soda, and as such its dissociation is far more complete in water than for Baking Soda, so if there is a "correction factor" I'm missing for Ca(OH)2 it will be magnitudes smaller than the (already rather small) adjustment factor for Baking Soda with respect to pH. Likely small enough to totally ignore.

 

[ajdelange]

The normality of the lime will not change appreciably with pH < 8 but we would, in a thorough treatment, have to consider the effects of a change in pH or of different alkalinity definitions on the source of the 30 ppm alkalinity. Were it all from Ca(OH)2 it would not matter but were it from bicarbonate, as in most cases it presumably is, it would (but not by much).

 

[Big Monk]

RPIScotty, Ca(OH)2 is a very strong base by comparison to the rather weak base that is commonly called Baking Soda, and as such its dissociation is far more complete in water than for Baking Soda, so if there is a "correction factor" I'm missing for Ca(OH)2 it will be magnitudes smaller than the (already rather small) adjustment factor for Baking Soda with respect to pH. Likely small enough to totally ignore.

Yes I stand corrected. I just peeked at the functions.