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1
Brewing Water
6 October 2008A.J. deLange
Burp Education Series
Based on class given 28 April 1996
2
Perspective• The community (and I) have learned a few things about brewing water
since 1996 (when I last gave this class) • Then: Slavish attention to reproducing brewing cities’ ion profiles
– A lot of people did a lot of hard work based on bogus data (published ion profiles)
• Now: Emphasis on getting proper mash pH with brewing liquor that more or less matches traditional profile
– Recognition of Residual Alkalinity as a powerful tool for evaluating and comparing brewing water samples
– Tweaking “stylistic ions” to taste (and authenticity).– Why put it in if you are just going to take it out (e.g. Munich Helles)?– Often no information whatsoever on type of water required for a particular
style - this is starting to change
• Most modern water supplies are generally good for brewing most beers.– Big Exception: Chloramine!!
Note: Red font denotes key concepts - take special note of these
3
Approach
• Water chemistry is intricate and detailed if not complex• In a couple of hours I can only skim the surface
– There won’t be time to thoroughly explain many of the concepts– Go back and look at the slides again at leisure– Some slides are in here with that intention - we won’t do much more than
mention them
• For practical knowledge you must explore further on your own– Papers on CD
• Most of the bloody details are found in the Cerevesia paper
– Spreadsheet on CD• This will be your best friend in terms of practical applications.
– Books (see list at end)– Internet
4
There are Two Aspects to Brewing Water
• I: Water chemistry has great influence on mash pH thus great influence on nature of the beer– Full understanding of this requires knowledge of acid-base
equilibrium chemistry, intricate calculations…• Reviewed in Cerevesia article (on handout CD)
– Fortunately, a simple (to use) Excel spreadsheet (on handout CD) can handle all of this for you
• You need to know how to use it and what the numbers mean - not how to program it
• II: Certain ions influence flavors - just as they do in any other form of cooking.– Salt to taste
5
Your Goals• Understand
– Relationship between beer and water it’s made from– Fundamentals of chemistry related to brewing water
• Atoms, molecules, ions, moles, equivalents, acids, titration…
– pH, Alkalinity, Residual Alkalinity (RA) and Hardness• These are the key concepts
• Be able to…– Read a water report
• Check it for validity (using spreadsheet)
– Treat water to • Remove chlorine and chloramine• Reduce bicarbonate (alkalinity) and iron (if you have it)• Control the pH of your mash• Establish an approximation to a desired ion profile
6
Quotations
• “Wine is made by farmers. Beer is made by engineers.” (?)• “A distinction is frequently drawn in the industry between
the theoretical man who tries to explain everything from a scientific point of view, and the practical man who relies on empirical knowledge and experience. A good brewer should be able to steer a middle course between these two extremes” - Jean deClerck
• “The third group, the smallest, are the Noonanians, the triple decoction cultists. Eighteen hour brew days, elaborate water modifications: you wonder how they stay married.” - Delano DuGarm
7
Quotations II
• Water contains three ions which influence the pH of wort: bicarbonate, calcium and magnesium. The bicarbonate ion has a pH raising effect, the other two lower it. The pH lowering effect of magnesium ions is only half that of calcium ions. Depending on the ratio of the water’s content of bicarbonate on the one hand and calcium and magnesium on the other, the pH raising effects of the bicarbonate is more or less compensated or balanced. Thus experiment has shown that to balance 1 equivalent of bicarbonate ion 3.5 equivalents of calcium or 7 equivalents of magnesium ion are required. With respect to the pH raising property of the total alkalinity of the brew water, thus, a definite part is balanced. The remainder, the residual alkalinity, can serve as a measure of the pH raising effect of the water.– Paul Kohlbach, Die Einfluss des Brauwassers auf das pH von Würze und
Bier, Monatsschrift für Brauerei, Berlin, Mai 1953 – Whole paper is on CD. Read it!
8
Topics
• Part 0: Beer and Water• Part 1: Fundamentals of Chemistry• Part 2: Carbon Dioxide, Water, Limestone, pH, Hardness,
Alkalinity• Part 3: Adding Malt Phosphate to the Picture , Residual
Alkalinity• Part 4: Water reports• Part 5: Water testing• Part 6: Water Treatment • Part 7: Synthesis of water with a given ion profile• Part 8: Comparison Beer
9
Handout CD Contains…• A copy of this presentation • Translation of Paul Kohlbach’s seminal paper (1953) • A set of slides from a lecture given at DeClerck Chair XI (Louvaine-
la-Neuve, Sept 2004)• Copy of the paper (based on that lecture) from Cerevesia 29(4) 2004• Microsoft Excel spreadsheet which implements the significant
brewing water chemistry calculations• Two part BT article on Alkalinity (unpublished)• BT article on Chloramine• New York Times Science article (geology and beer).• 54 recipes for water of various brewing cities from common salts
and distilled water.
10
Part 0Overview - Beer and Water
11
Water and Beer Style
• Water is heavy (1 kg/L ~ 8.3 Lbs/gal.)• Barley, malt and hops can be cost effectively
moved fairly long distances - water can not.• Therefore, absent ability to treat it, local water
determined what local beer was like– Soft water: Bohemian Pils– Hard, bicarbonate Water: Munich Dunkles, London
Ales• Remove bicarbonate and you can make Helles
– Hard Sulfate Water: Burton Ales
12
The First of the Two Aspects• Bicarbonate is a base - it’s alkaline
– It raises mash pH ~ malt enzymes become less effective– It must be neutralized or removed (so pH is kept low)
• Hardness (Ca++, Mg++) plus malt phosphate neutralize it – Alkalinity (water bicarbonate) not neutralized by water hardness +
malt phosphate is called Residual Alkalinty
• Acid neutralizes it– Sulfuric, hydrochloric, lactic, acid in dark malt
– High alkalinity water requires lots of hardness, acid and or dark malt to neutralize it (and conversely)
• Theme: Contest between alkalinity (bad) and hardness (good) for control of mash pH.
13
Hardness & Alkalinity for Several Cities
RA = Alkalinity - (Ca_hardness + Mg_hardness/2)/3.5
Good
Bad
OK
OK
14
Part 1 Fundamentals of Chemistry:
Atoms, Molecules, Ions, Acids, Bases
15
For Further Information…
• We can only skim (rapidly) the surface at the highest level today
• Nothing here beyond college freshman chemistry– Should today stimulate your interest, review freshman
chemistry or biochemistry text• Pay particular attention to ionic equilibrium (law of mass
action), acid/base chemistry, Henderson Hasselbalch equation.
– Read Cerevesia article on CD
16
Atoms• Smallest particle of elemental matter with nucleus of positively
charged protons and uncharged neutrons…– … of mass ~1.673E-24 grams (protons and neutrons slightly different)
• Surrounded by negatively charged electrons– With mass 0.000911E-24 grams (1/1822 of proton)– Number of electrons equals number of protons– Atom has a net charge of 0.– Electrons group into shells– Most of the elements we’ll deal with like to have 8 electrons in outer shell
• The number of protons (and electrons) determine which element the atom is
– 1: H, 2: He, 3: Li, 4: Be, 5: B, 6: C 7: N, 8: O 9: F, 10: Ne
• Number of neutrons determines which isotope– 6 protons + 6 neutrons ~ 12C (normal); 6p + 8n ~ 14C (radioactive)
17
Chemical Symbols• Each element (atom type) is represented by a symbol
– It’s often pretty obvious which element is meant…• H ~ Hydrogen C ~ Carbon O ~ Oxygen Ca ~ Calcium Mg ~ Magnesium S ~
Sulfur– But not always…
• Na ~ Sodium (L. Natrium) K ~ Potassium (L. Kalium) Fe ~ Iron (L. Ferrum) Hg ~ Mercury (L. Hydrargyrum)
• Combined atom symbols represent compounds:– NaCl ~ Sodium chloride HCl ~ Hydrochloric Acid CaCl2 ~ Calcium chloride
H2CO3 ~ Carbonic acid CaCO3 ~ Calcium Carbonate CaSO4.2H2O Calcium Sulfate with 2 waters of hydration.
– Subscript indicates number of atoms in molecule• 1 Molecule of CaCO3 has 1 calcium, 1 Carbon, 3 Oxygen atoms
• Ion (electrically charged atom or molecule) is indicated by element or compound symbols with charge shown– Na+ ~ Sodium ion Ca++ ~ Calcium ion HCO3
- ~ Bicarbonate
18
IONS• Noble gasses Helium, Neon, Argon… have complete electron
shells ~ chemically stable• Atoms may take on or release electrons to complete or leave a
complete shell– Sodium ([Ne]+1e-): Na --> e- + Na+ Sodium Ion
– [Noble gas] represents the electronic structure of that gas
• Giving up 1 electron leaves Neon (10 e-) shell structure• Could give it to e.g. chlorine…
– Chlorine ([Ne]+7e-): Cl + e- --> Cl- Ion • ([Ne]+8e- = [Ar])
– Calcium ([Ar]+2e-): Ca --> 2e- + Ca++ Ion• Take away 2 electrons leaves Argon shell structure
– Hydrogen (1 e-): H --> e- + H+ Hydrogen Ion• Naked proton (quickly attaches to a water molecule)
19
Molecules• Atoms can also share (or give) electrons with (to) other atoms
in order to complete shells – Carbon (C) has 4 electrons in its outer shell: [He]+4e-
– Hydrogen (H) has 1 electron: 1e- – If carbon shares the electrons from each of 4 hydrogen atoms it
completes its outer (valence) shell :• [He] + 4e- + 4e-(shared from hydrogens) ~ [Ne]
– Each hydrogen shares one of carbon’s electrons• 1e- + 1e- (shared from carbon) ~ [He]
– CH4 is the gas methane
• Na gives e- to Cl. Na+ attracts Cl- --> NaCl• Atoms so combined are called molecules the constituents of
compounds.
20
Dissociation
• Some molecules (acids) may release or take on (bases) protons (hydrogen ions) thus becoming ions themselves– Carbonic Acid: H2CO3 --> H+ + HCO3
- Bicarbonate ion– Ammonia (base): NH3 + H+ --> NH4
+ Ammonium ion– Sulfuric Acid: H2SO4 --> H+ + HSO4
- Bisulfate ion– Hydrochloric Acid: HCl --> H+ + Cl- Chloride ion
• Ions can do this too and become doubly ionized or un-ionized– Bicarbonate ion: HCO3
- --> H+ + CO3-- Carbonate ion
– Bicarbonate ion: HCO3- + H+ --> + H2CO3
Carbonic acid
• Molecules (or ions) which give up protons are acids in the Lowry-Brønstead sense (there are other definitions)
• Molecules (or ions) which take up protons are bases in the Lowry-Brønstead sense.
21
Chemical Equations
• Reactants on left, products on right• Equation in the sense that numbers of atoms (of each type) and charges
must be equal on each side• Ca(OH)2 + Ca++ + 2HCO3
- --> 2CaCO3 + 2H2O– This says that 1 molecule of calcium hydroxide (slaked lime) reacts with 1
calcium ion and 2 bicarbonate ions producing 2 molecules of calcium carbonate (chalk) which precipitates (underbar) and 2 molecules of water
– 2 Calcium, 2 Carbon, 8 Oxygen, 4 Hydrogen, 0 charge on each side– --> indicates that reaction proceeds from left to right but not in other direction
(many, indeed all, reactions proceed in both directions if conditions are right but one is sometimes preferred.)
• This reaction is commonly used by brewers to remove bicarbonate from alkaline water.
• Because it removes calcium, a component of hardness, as well it is usually thought of as a “water softening” treatment.
22
Measurement of Chemicals• RE last slide: each molecule of lime will remove 2 bicarbonate ions.
How much lime do we need to buy to process x gallons of water?• Clearly we need to have some idea of what a molecule weighs and
how many we need.• Molecules, like atoms and ions, are made up of protons and
neutrons which contribute nearly all the weight as electron weight is negligible
• One proton weighs 1 Dalton (1 Atomic Mass Unit)• How many protons weigh one gram?
– Answer: 6.023E+23 called Avogadro’s Number.– Avogadro’s number of Daltons = 1 gram– Avogadro’s number of anything (atoms, molecules, ions, electrons, rutabagas,
even furry blind subterranean mammals) is called one mole
23
Gram Molecular Weights ~Weight of 1 mole
• Hydrogen: 1 proton. 1 mole should weigh about 1 gram. Actual GMW 1.00794• Oxygen: 8 protons, 8 neutrons. 1 mole should weigh about 16 grams. Actual value
15.9994• Calcium: 20 protons, 20 neutrons. 1 mole should weigh about 40 grams. Actual
value 40.078• Ca(OH)2: 38 protons, 38 neutrons. 1 mole should weigh about 74 grams. Actual
GMW 74.093• HCO3
-: 31 protons, 30 neutrons. 1 mole should weigh about 61 grams. Actual GMW 61.03
• Thus 1 molecule of Ca(OH)2 reacting with 2 HCO3- ions implies that 6.023E23 (1
mole = 74.093grams) of Ca(OH)2 will react with 12.046E23 (2 moles = 122.06 grams) of HCO3
- and so on in that proportion• Example: To decarbonate water with 61 milligrams (mg) of bicarbonate (1
millimole) per liter would require 1/2 mMol of Ca(OH)2 weighing 74.093/2 = 37.046 mg per liter.
24
Equivalent Weight• Sometimes specified weights are based on moles of charge rather than moles
of ions or atoms
• Singly charged HCO3-: 31 protons, 30 neutrons. GMW 61.03 means 61.03
grams has a charge of 1 mole of (-) charges. Equivalent weight = 61.03.
• Doubly charged Ca++: 20 protons, 20 neutrons. GMW 40.078 means 40.078 grams carries 2 moles of (+) charge. 20.039 grams carries 1 mole. Equivalent weight = 20.039
• Equivalent weight = gram molecular weight divided by charge.
• Alkalinity (HCO3-) and hardness (Ca++, Mg++) are often expressed in
milliequivalents per liter (mEq/L sometimes called mVal/L or just mVal).
• Sometimes given as 50 times mEq/L - called parts per million as CaCO3
– This is seen a lot. Note: 1 ppm ~ 1 mg/L (as water weighs ~ 1 kg/L)
CaCO3 + CO2 + H20 --> 2HCO3- + Ca++
100mg1mMol
44mg1mMol
18mg1mMol
122mg2mMol
2mEq100ppm asCaCO3
40mg1mMol
2mEq100ppm asCaCO3
25
Example of Calculation• Being an environmentally conscientious brewer you wish to neutralize your standard lye
cleaning solution (1 pound lye in 5 gal water) before dumping it down the drain. How much acid is needed?– Na(OH) + H2O --> Na+ +(OH)- + H2O
• Lye GMW 40: 1 lb = 454 g ~ 454/40 = 11.36 Mol ~ 11.36 Eq (OH)-
• H+ + (OH)- --> H2O Need 11.36 Eq H+ • Sulfuric Acid MW 98: H2SO4 --> 2H+ + SO4
--
– 11.36/2 Mol H2SO4 yields 11.36 Eq H+ – 98*11.36/2 = 556 grams ~ 1.23 lbs concentrated sulfuric acid required.– 11.36 Mol of Na+ & 11.36/2 Mol SO4
-- (11.36/2 Mol Na2SO4, MW 142 ~ 11.36*142/2 = 0.806 kg) go down drain (wrong on CD)
• Hydrochloric Acid MW 36.46: HCl --> H+ + Cl-
– 38% HCl solution (23 Baume) is 12.29 Normal meaning it contains 12.29 Eq H + per litre. Therefore need 11.36/12.29 = 0.917 L of 38% HCl
– 664 g NaCl (table salt) goes down drain
• Add acid to solution until pH neutral rather than relying on calculation
26
Another Example Calculation
• Water tests 3 mg/L available chlorine (from chloramine). How much potassium metabisulfite (K2S2O5 MW 222.32) is required to treat 20 gal (76 L)
– 2K+ + S2O5-- + 2H2NCl + 3H2O --> 2K+ + 2SO4
-- + 2H+ + 2Cl- + 2NH4+
– Each mole of chlorine requires 0.5 mole of bisulfite ion and produces 1 mole of sulfate, 1 equivalent of hydrogen ions, 1 mole of chloride ions and 1 mole of ammonium ions.
– 3 mg/L Cl ~ 3/35.45 = 0.0846 mMol/L requiring 0.0423 mMol/L metabisulfite and producing 0.0846 mMol/L sulfate, hydrogen, chloride and ammonium ions.
– The GMW of potassium metabisulfite is 222.32 mg/mMol so we need 9.4 mg/L or 714 mg total (one lot of Campden tablest we measured weighed 695 mg)
– The hydrogen ions, 0.0846 mEq/L represent a reduction in alkalinity of 50 times this or 4.2 ppm as CaCO3.
– As each bound chlorine atom is converted to a chloride ion the chloride level will increase by 3 mg/L
– 0.0846 mMol/L * 96 mg/mMol ~ 8.12 mg/L increase in sulfate (Pils brewers take note)– 0.0846 mMol/L*18 mg/mMol ~ 1.5 mg/L increase in ammonium ion (your yeast will
love it)
27
Part 2Carbon Dioxide, Water & Limestone; Hardness &
Alkalinity
28
Carbon Dioxide: CO2 MW 44.01• Spewed by volcanoes• Taken up by plants -> sugar, starch… oxygen
– 6CO2 + 6H2O ------> C6H12O6 + 6O2
• Released by carbohydrate oxidation (including respiration, fermentation, decay…)– CnH2nOn + nO2 --> nCO2 + nH2O
• A greenhouse gas – Though not a very effective one (10% re water vapor)
• Present in the atmosphere to the extent of 0.03% (0.0003Atm ~ 0.3 hPa)• Absorbed/released by oceans, rivers, lakes
– Sequestered by animals which build shells from it
• Dissolves in water to form carbonic acid which, in turn, dissolves limestone– This is the property of significance to brewers (and spelunkers).
light
29
Water• Continuous cycle of evaporation, condensation, precipitation…• Ultimately comes to us from rain, snow, meltoff..
– Runs over surface of earth into a stream/pond…• In equilibrium with atmospheric CO2
• Leaches substances from surface organic/inorganic materials with which it comes in contact
– Or percolates into ground and is withdrawn from well penetrating aquifer• In equilibrium with subterranean CO2 (respiring bacteria)• Typically more acidic (dissolved CO2)• Dissolves minerals from rock with which it comes in contact
– Limestone caves• Typically more mineral content than surface water• Usually clearer, fewer bacteria than surface (well filtered)• May be in the ground for years.
30
Carbonic Acid MW 62.03• CO2 dissolves in water to form carbonic acid…
– CO2 + H2O <--> H2CO3*
– * indicates this is both dissolved but not hydrated CO2 and hydrated CO2
– Arrow is two headed. Carbonic acid can decompose into water and CO2
• … which can give up a proton to form bicarbonate ion…– H2CO3
* <--> H+ + HCO3-
– Ability to give up proton defines H2CO3 as an acid– In reverse, HCO3
- can take up a proton to form H2CO3. This defines a base
• …which can give up its proton to form carbonate…– HCO3
- <--> H+ + CO3--
– The fact that it does so defines bicarbonate as an acid.– Thus bicarbonate is an acid and a base (it is amphoteric)
• Which it behaves as depends on pH (at brewing pH it is basic)
– In reverse, CO3-- takes up a proton to form HCO3
- . CO3-- is a base
• …which can coalesce with calcium ion to precipitate chalk– CO3
-- + Ca++ <--> CaCO3 (only slightly soluble)
31
Calcium Carbonate MW 100.087• Ca++ + CO3
-- --> CaCO3 (lime, chalk, limestone)– Happens in the bodies of marine animals– Main source of limestone - sequesters CO2, sends to bottom– 10% of all sedimentary rock
• Happens when hard bicarbonate water is heated– Popular method for decarbonating brewing water
• Or when hard bicarbonate water evaporates– Shower heads– Stalactites/Stalagmites
• Dissolved by carbonic acid - source of calcium hardness– CaCO3 + H2O + CO2 --> CaCO3 + H2CO3 --> 2HCO3
- + Ca++
– Surface and ground water are hard & alkaline
– Cave formation: underground paCO2 much higher (hence more carbonic) because of
respiring bacteria
32
Law of Mass Action• In any reaction mA + nB <--> kC + jD • {C}k{D}j/{A}m{B}n = K, a constant (constant temp.)
– {A} = activity of A– For a gas {A} is approximately the partial pressure– For a dissolved substance {A} is approximately the concentration (moles per liter)– For a solid {A} = 1
• Define p{A} = - log10{A}• Then kp{C} + jp{D} - mp{A} - np{B} = pK• If A + B <--> C (underscore ~ precipitation) then
– {A}{B} < Ks (solubility product) No precipitation occurs– {A}{B} > Ks supersaturated. Precipitation usually occurs– {A}{B} = Ks saturated. No precipitation– p{A} + p{B} = pKs at saturation
33
Carbonic - Loss of 1st Proton• H2CO3
* <--> H+ + HCO3-
• {H+}{HCO3-}/{H2CO3
*} = K1
• pH + p{HCO3-} - p{H2CO3
*} = pK1
– Henderson-Hasselbalch Equation – p{x} = - log x– p{H+} = pH is special - more to follow on this
• pH - pK1 = p{H2CO3*}- p{HCO3
-}– rearranged
• 10 pH - pK1 =10p{H2CO3
*} - p{HCO3
-} = {HCO3-} / {H2CO3
*} = r1
= ratio bicarbonate to carbonic– Took antilog of both sides– Note if pH = pK1 then r1 = 1; {HCO3
-} = {H2CO3*}
34
Carbonic - Loss of 2nd Proton
• HCO3- <--> H+ + CO3
--
• {H+}{CO3--}/{HCO3
-} = K2
• pH + p{CO3--} - p{HCO3
-} = pK2
• pH - pK2 = p{HCO3-}- p{CO3
--}
• 10 pH - pK2 =10p{HCO3
-} - p{CO3
--} = {CO3--} / {HCO3
-} = r2 = ratio carbonate to bicarbonate
• If pH = pK2 then r2 = 1; {CO3--} = {HCO3
-}• Solutions tend to resist pH changes near their pK’s
– This is called buffering
35
H2CO3, HCO3-, CO3
-- Fractions
• If there are x moles of carbonic, there are r1x moles of bicarbonate and xr1r2 moles of carbonate for a total of CT = x(1 + r1 + r1r2) =xd
• CT = total carbo• The fraction which is carbonic is x/xd = 1/d = f1
• The fraction which is bicarbonate is r1 times this = r1/d = f2
• The fraction which is carbonate is r2 times this or r1r2d = f3
36
Distribution of carbo species1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
121110987654
pH
Distribution of CARBO as a function of pH
CARBOnic biCARBOnate CARBOnate
Fractions.EPSF
pHs
Alkalinity is defined as the number of mEq of acid required to change the pHof a sample from its pH at the source (pHs) to pH 4.3
pK1
6.38
pK2
10.35
37
Alkalinity
• Definition: the number of mEq of acid required to change pH of a sample to a reference pH (usually pHr = 4.3)– Sum of
• Acid required to change carbonate to carbonic• Acid required to change bicarbonate to carbonic• Acid required to increase {H+} to (1000)10-pHr mEq/L• Acid require to neutralize (OH)-
• r ~ reference pH, s ~ sample pH, pKw = 14• Units: mEq/L (that’s why the factor of 1000 is there)• CT = total mmol/K carbonic, bicarbonate, carbonate• Equation can be solved for CT if alk, pHr and pHs are known• Thus choice of pHr is somewhat arbitrary
alk = CT(f1,r - f1,s + f3,s- f3,r) + (1000)10(pHs-pHr) + (1000)10(pKw-pHr-pHs)
38
Solubility Product• {Ca++}{CO3
--}< Ks Solubility Product– If {Ca++}{CO3
--} = Ks water is called saturated
• p{Ca++}+p{CO3--}< pKs
• Calcium carbonate is not very soluble in water• To precipitate carbo (and hardness) establish conditions
which violate inequality– Increase pH & thus f3 (Drive off CO2 by heat, sparge)– Decrease Ks (raise temperature)– Increase {Ca++} (add gypsum or CaCl2)– Combinations (Ca(OH)2 increases pH and {Ca++})
39
Combine Equations• Add Eqns for dissolving CO2, CaCO3 saturation, water
dissociation and electric neutrality
• CO2 Dissolves:
• A proton is lost:
• A 2nd proton is lost:
• CaCO3 Saturation:
• Water dissociates:
• The total charge is 0:
• Define:
• Substitute into charge neutrality equation,
• Solve (root finder) for pH which satisfies this equation
• Substitute back
€
p H2CO3[ ] − pPCO2= pK H
€ € €
pH + p CO3−2
[ ] − p HCO3−
[ ] = pK2 − 3pfm
€
pH + p HCO3−
[ ] − p H2CO3[ ] = pK1 − pfm
€
p Ca+2[ ] + p CO3
−2[ ] = pKS − 8pfm
€
pH + p OH−[ ] = pKW − pfm
€
2 Ca+2[ ] +10− pH − HCO3
−[ ] − 2 CO3
−2[ ] −10− pKW − pH( ) = 0
€
r1 =HCO3
−[ ]
H2CO3[ ]=10 pH − pK1 + pfm( )
€
r2 =CO3
−2[ ]
HCO3−
[ ]=10 pH − pK2 +3 pfm( )
pfm accounts for fact that solutions are not “ideally dilute”. We will ignore this.
40
Why All this Horrible Math?
• It is what allows us to …– Validate a water analysis– Calculate alkalinity and estimate the acid required for
proper mash pH– Synthesize any water ion profile from any starting water
(e.g. salt additions to get Burton water from my well water)
– Determine whether water is stable (saturated with respect to CO2 or CaCO3
– Make charts like one on next slide
• It is what is behind the spreadsheet on the CD
41
CO2 Over Water in Equilibrium with CaCO3
42
Review - Dissolving Limestone
HCO 3""1–H2CO 3
CO 2
CO 32–
CaCO 3
Ca +2
58.5 0.38
230.8 0.095
r1=70.8 r2=.0065r1=4.5 r2=.0004
H+
H2O (OH)-
pKH
pK1pK2
pKS
pKw
H2O
.0004
.025
17.5
80.3
pH 7
pH 8.3
Partial Pressureof CO2, Atmospheres
0.84
52.5
Concentrations,mg/L
Gas Phase
Liquid Phase
Solid Phase
Alkalinity comes from limestone and the carbonic acid whichIs required to dissolve it.Calcium hardness comes from dissolved limestone.
43
pH• Søren Peter Lauritz Sørenson (1868 -1939)
– Worked at Carlsberg Laboratory– Studied amino acids, proteins enzymes– Their behaviour (total electric charge) depends on hydrogen ion
concentration (mechanism we’ve been discussing).– Sought convenient scale for specifying {H+} (1909)– Called it pondus (L. a weight) hydrogenii i.e. pH = -log10{H+}– For pure water {H+} = 10-7 Mol/L thus pH = 7– For .001 N acid {H+} = 10-3 Mol/L thus pH = 3
• pH < 7: Acid, sour, beer, wine, soda (phosphates), vinegar, lemon, lime (citrus), sauerkraut, sour cream, kimche
• pH ~ 7: Neutral, water, blood, brine• pH > 7: Base, bitter, lye, lime (slaked), soda ash
44
Importance of pH in Brewing• Necessary to calculate carbo species distribution in water
• As pH changes charge distribution on proteins it changes conformation of enzymes
– Brewing water treatment is done to get enzymes properly conformed for protein lysis, starch to sugar conversion…
– Happens in range pH 5.2-5.7
• Proper charge distribution on proteins (chains of amino acids) in boil (iso-electric point~ net charge 0) enhances coagulation
H3N+CRHCOOH H3N
+CRHCOO- H2NCRHCOO-
H+ H+
pH 1 Q = 1 pH 6 Q = 0 pH 14 Q = -1
Charge (Q) shown for simplest amino acid, Glycine (R = H)
Note: For some amino acids (Arginine, Lysine, Tyrosine….) R may be ionizeable in which case other charge values are possible
45
Importance of pH II
• Tanins not extracted from barley husks if sparge pH < 6• Yeast produce acid to kill competing organisms
– Thus pH drop is first sign of healthy fermentation
• pH has an effect on stability of colloids in finished beer.• pH modulates formation of melanoidins• IOW, each part of the brewing process proceeds best in a
range of pH (and temperature)– XI DeClerck Chair: 3 Days of lectures on “pH Paradox” devoted
to this subject
• Advanced brewer feels as helpless without his pH meter as he does without his thermometer.
46
pH Measurement• Originally with dye which changes color at particular pH
– “Litmus Test” from a lichen (red < 7, blue >7)– Phenolpthalein, bromcresol red, methyl orange (4.3) …
• Electronically: potential developed across specially prepared (delicate) glass bulb dependent on pH difference between inside and out
– Potential measured between electrode inside bulb and reference junction electrically connected to solution being measured (outside bulb)
– Very feeble current. Extremely high impedance amplifier required– 57 millivolt change per unit pH change
• Depends on temperature - temperature compensation essential• Note: pH also changes with temperature (because pK’s do). This is a separate effect
• Special field effect transistors (ISFET)– Much more durable, store dry
• Modern meters more dependable, last longer, less expensive, feature rich (ATC, auto buffer recognition) but still not for the casual user.
• Must be calibrated frequently with buffers of known pH
47
Part IIIAdding Phosphate, Residual
Alkalinity
48
Phosphoric Acid Chemistry
• Same as carbonic except– The oxide is a solid: P2O5 + 3H2O --> 2H3PO4
• Compare: CO2 + H2O --> H2CO3
• General reaction for oxoacids– Includes carbonic, phosphoric, nitric, sulfuric
– Three protons:• H3PO4 --> H+ + H2PO4
- --> 2H+ + HPO4-- --> 3H+ + PO4
---
• Three (not the same as carbonic) pK’s (2.12, 7.21, 12.67), three r’s, three f’s.
• Calcium phosphate is very insoluble– The smallest amount of phosphate will pull out lots of calcium– This is why trisodium phosphate was used as water softener
• 3Ca++ + 2Na3PO4 ---> Ca3(PO4)2 + 6Na+
– And why malt phosphate lowers pH of hard water• Net reaction releases protons (hydrogen ions) - later slide
Phytic Acid from Malt
49
50
Malt Phosphate• Up to 2% of malt weight is phosphate
– In the form of phytin, salt of myoinositol hexaphosphate
• Enzyme phytase breaks down phytin releasing inorganic phosphate (H2PO4-,
HPO4--) and B vitamin myoinositol (good for yeast)
– Phytase survives only mild kilning i.e. active in pale base malts only
• Phosphate coalesces with any calcium in water, precipitates and releases protons which lower mash pH.
• Paul Kohlbach observed that 3.5 mEq of Ca++ or 7 mEq Mg++ “neutralize” 1 mEq alkalinity
– Neutralize here means that the pH of a mash with all alkalinity neutralized has same pH as a distilled water mash (~ 5.7)
– Defined Residual Alkalinity: RA = alk. -({Ca++} + {Mg++}/2)/3.5• Alkalinity, hardnesses and residual alkalinity all in units of either mEq/L or ppm as
CaCO3.
– Also noted 0.085 pH shift for each mEq/L (50 ppm) of RA
51
Residual Alkalinity Chart
• Residual Alkalinity: RA = alk. -({Ca++} + {Mg++}/2)/3.5• Define Hard_eff = -({Ca++} + {Mg++}/2)
– Effective hardness equals calcium hardness plus half magnesium hardness
• Then RA = alk. - Hard_eff/3.5• Solve for alk: alk = RA + Hard_eff/3.5• Plotting alk vs. Hard_eff for a given RA gives a straight line which
crosses the alk axis at RA and has slope 1/3.5• This is the chart from earlier in the presentation• RA values in increments of 50 ppm as CaCO3 corresponding to pH
shift increments of 0.085• Above heavy line (RA = 0) pH will be higher than distilled water
mash, below it, pH will be higher• RA < 50 generally OK (dotted line)
52
RA Chart
53
Use of Chart - Example• Edinburg (Edn2): Alk 180, Hard_eff 340, RA 85, pH ~
5.89 is too high• Reduce alkalinity by 180 - 100 = 80 to get to RA ~ 0
and pH ~5.75– Add 80/50 = 1.6 mEq/L acid (e.g. HCl, H2SO4)– Decarbonate water. Can get to approximately 50 ppm as
CaCO3, RA ~ 35, pH 5.69• Could also get to this RA by adding (180 -50)/50 = 2.6 mEq/L acid
• Add (620 - 340)/50 = 5.6 mEq/L hardness– 5.6 mEq/L Ca++ ~ 2.8 mMol/L CaSO4.2H20 ~ 482 mg/L
gypsum
54
Carbo + Phosphate System
HCO 3""1–H 2CO 3
CO 2
CO 32–
CaCO 3
Ca +2
H +
H +
H+
H+
H+
H+
H3PO 4 H2PO 41– HPO 4
2– PO43–
Ca 10 PO 4() 6 OH() 2
87.6% 12.4% .0002%
.04% 98.0% 1.95% <.00001%
18.3% 81.7% .04%
.0008% 61.3% 38.7% .001%
% T otal CO3 5.5@pH
7.0@pH
% T otal PO4 5.5@pH
7.0@pH
r1=0.14r2=1.4E-5
r1=2398r2=.02 r3=1.1E-7
r1=4.46r2=4.5E-4
r1=75857 r2=0.631 r3=3.6E-6
H2O (OH)-pKw
H2O
pKwCa+2
(OH)-
pKsC
pKsP
10Ca+2+12HCO3- + 6H2PO4
- + 2H2O -> Ca10(PO4)6(OH)2 + 12CO2+ 2H+ +12H2O
Demonstration• Prepare phosphate buffer from 40 mMol/L KH2PO4
• Add Na2HPO4 to pH 5.92– Phosphate buffers very commonly used to control pH in laboratory
• Simulates phosphate distribution in distilled water mash• Add strong CaCl2 solution drop by drop and observe pH• pH falls gradually at first, then as precipitate (hydroxyl apatite)
forms, more rapidly• This is the mechanism by which hard water produces acid to
neutralize alkalinity– There is no alkalinity here (buffer made with distilled water)
– Were alkalinity present, pH drop would no be so dramatic as some of the H+ released would go to neutralize it.
55
56
Part IVWater Reports
57
Water Report Key Parameters1st Aspect
• Alkalinity– Measure of acid required to lower sample pH to 4.3 ~ buffering capacity of water– Indicator of amount of acid (from any source) required to establish proper mash
pH (5.2-5.6)– Measure of bicarbonate content
• Hardness– Measure of amount of calcium and magnesium in sample.
• Mg++ and Ca++ should be measured and reported separately– Indicator of extent to which water is capable of offsetting it’s alkalinity (reaction
with malt phosphate)
• pH– Permits calculation of ion balance (quality check on report) – Permits calculation of amount of bicarbonate from alkalinity– Otherwise, not really that important
58
Water Report Key Parameters 2nd Aspect
• Sulfate– Large effect on the way hops are perceived
• High value for assertive, dry hop flavor• Low (15mg/L or less) for beers using a lot of noble hops
• Sodium– Leads to salty taste in high concentrations
• Chloride– Leads to salty taste in high concentration, “pasty” in very high >300mg/L– Lends round, sweet quality in modest amounts
• Iron– The less the better - tinny, “inky”, metalic taste
• For Brewing, < 0.1 mg/L ; EPA secondary limit < 0.3mg/L
• Copper– Metalic taste. May indicate pipe corosion
• Need a small amount. Yeast enzyme co factor
• Chlorine and, in particular, Chloramine– Chloramine forms ppb detectable chlorphenolics (plastic taste)
59
Calcium• Most important brewing ion?
• From dissolved limestone, gypsum
• Important enzyme co-factor– Protects -amylase from heat
– Stimulates proteolytic and amylitic enzymes
– Reaction with phytin lowers mash pH
• Favors rapid, bright runoff
• Facilitates break formation
• Improves yeast flocculation
• Precipitates oxalate in beer (enhanced clarity)
60
Magnesium
• Part of hardness - half as effective as Calcium in RA reduction (mEq for mEq).
• Laxative above 120 ppm esp. with SO4--
• Sour/bitter quality at > 30 ppm– Hence remove if above this level by split treatment (to be covered)
– Not a problem with local (DC area) water
• There are claims that it lowers cardiac mortality
61
Sources of Water Reports• Your supplier (municipality, water company…)
– Go to its website, call or visit the office– You are likely to get a lot of promotional material about DBP rule,
cryptosporidium, industrial contaminants etc.– Persist until you get an inorganic report including alkalinity and hardness
• Tell them that you are a brewer and this is what you need• In earlier days some suppliers were reluctant to release information. Rare today
– May not be timely e.g. summary for 2008 may not publish until 2009• Test results from commercial lab (individual or community well owners)
– Make sure you get an inorganic analysis• Organic and microbiological tests important too but not for your brewing
needs– Ask other brewers (Ward Labs seems good)– Look in yellow pages/on web
• Results from tests you do yourself• Profiles published in books, articles, papers, …
62
63
April: 50*32.5/20 (Ca) + 50*8.2/12.15 (Mg) = 80 + 33.7 = 113.7 total hardness. Compareto April total and calcium hardness numbers on previous slide. Could be different methods(e.g. AAS) samples taken on different days etc.
64
65
Imbal =100*(1.4-1.1)/(1.4+1.1)=12%
66
Water Report QA Check• Any water report should be checked for internal
consistency– Especially ones done by yourself or a lab– Lab often includes QA check as part of its report
• Check based on electrical neutrality i.e. sum of charges on anions should equal sum on cations.– As relative numbers of carbonic (0), bicarbonate(-1) and
carbonate(-2) depend on pH calculation gets a bit nettlesome• Must calculate CT, r’s, f’s
– Spreadsheet on CD takes care of all this for you• Full instructions for use on 2nd sheet.
67
Available WaterpH 6.00 4.300 End Point pHTemp + for C, - for F 20.0 20.0 Temp, CTemp K 293.20 293.20pK1 6.38 6.38pK2 10.38 10.38pKw 14.16 14.16A 0.714r1 0.42 0.01r2 0.00 0.00f1 = 1/d 0.71 0.99 Bicarb. @ pHa [H+] @ pHa Differencef2 0.29 0.01 0.034 0.050 -0.016f3 0.0000 0.0000f1 + f2 + f3 1.00 1.00No carb alkalinity 0.0491
Alk, + as CaCO3, - mEq/L 62.00Ca, + as CaCO3, - as mg/L 71.00Mg, + as CaCO3 - as mg/L 48.00Alk, mEq/K 1.24000 Gram Eq. Wt Cations Anions
28.4568 <-- mg/L Ca mEq/L--> 1.42 20.04 1.42011.6664 <-- mg/L Mg mEq/L--> 0.96 12.15 0.960
Rough Carbo 4.17535Rough Carbonic 129.81 0.000Rough Bicarbonate 74.73 61.03 Rough Carbonate 0.01 30.02 Total Carbo, mMol/L 4.16054H2CO3, mg/L 129.35H2CO3,mg/L 74.50 1.221CO3--,mg/L 0.00 0.000H+ 0.00 0.001(OH)- 0.00 0.000Sulfate. mg/L 20.40 48.04 0.425Chloride, mg/L 7.00 35.45 0.197Nitrate, mg/L 0.00 62.00 0.000Nitrite, mg/L 0.00 47.00 0.000Sodium, mg/L 0.00 22.99 0.000 Potassium, mg/L 0.00 39.10 0.000Fe(II), mg/L 0.00 27.92 0.000Fe(III), mg/L 0.00 18.62 0.000
Free Ammonia, mg/L 0.00 32.01 0.000 23173.174
Charges 2.381 1.843Imbal 0.538Imbal % 12.74%
Alkalinity 62.00Ca Hardness, as CaCO3 71.00Mg Hardness, as CaCO3 48.00
Total Hardness, as CaCO3 119.00
Residual Alkalinity 34.86 ppm as CaCO3Residual Alkalinity 0.70 mEq/L pH Shift RE Distilled Water 0.06
Ionic Strength, non carbo 2.90 Ionic Strength, carbo 0.61224Total Ionic Strength 3.52pfm 0.0392 0.0358910 pfm, no carbo
Data entry in clear cells.
Calculated results incolored cells
Result in red cell shouldbe < 10%
68
Full set of measurements from6341 Georgetown Pike well30 Oct 2008
69
Worksheet for 30 Oct 08Analysis
70
Part VTesting Water
71
Why Discuss Testing
• Test principals build on many of the things you have learned and most important test (alkalinity) mimics what happens in mash– Acid is added causing pH to drop
– This is why alkalinity is a useful measure
• Explanation of how test is done will enhance your understanding of what the parameter means
• You may wish to do some testing yourself– Only way to get a feel for extent of temporal variation in your supply
• Most tests relatively easily carried out with kits
– Get these from www.hach.com or aquarium supply company
– These things are getting expensive!
pH (Water Analysis Perspective)• Need to measure/detect “end point” pH in
alkalinity titration– This can be done with indicator dyes but woe betide the
color blind (your instructor)
– Electronic means more accurate, even for non Daltonians
– Electronic meters now more reliable, inexpensive, durable, feature laden than before
• But be kind to your pH meter. Keep it clean and wet. Don’t stick it into hot wort or mash!
72
pH Meter• Voltage E = E0 + (RT/F)ln{H+} is developed across special
glass membrane– E0 is voltage developed when {H+} = 1
– R (Bolzman’s) and F (Faraday’s) are constants
– T is temperature (Kelvins)
• E = E0 + 2.303(RT/F)log{H+} = E0 - S*pH
• You (or the meter), must know E0 and S in order to determine pH = (E0 –E)/S
• This is where standard buffers come in– Placing the meter in 2 solutions of known pH and at known
temperature allows meter to calculate S and E0• Thereafter meter can adjust readings for temperature response of electrode
(ATC)
• But not, e.g. shift in wort pH from kettle to room temperature! 73
74
Alkalinity
• Defined as the number of mEq/L of acid required to lower pH of water sample from its initial value, pHi, to a reference pH, pHa
• pHa is part of definition of alkalinity and is usually 4.3 in brewing– May be based on equivalence: CTf2,a ≈ (1000)10-pHa
– Analyst should report pHa. If he didn’t use 4.3– Important because you will solve for CT in report quality checking, synthesis
• Units of mEq/L (hence factor of 1000). Multiply by 50 for ppm as CaCO3.• CT = total millimoles/L carbonic, bicarbonate, carbonate in sample• f s subscripted i refer to fractions at pHi
• f s subscripted a refer to fractions at pHa
• Kw is dissociation constant of water (pKw = 14 @ 20°C)• Equals sum of acid required to
– Convert initial fractions to fractions (mostly carbonic) at pHa
– Increase hydrogen ion content to 10-pHa
– Decrease (by neutralizing to H2O) hydroxyl ion concentration to 10pHa-pKw
alk = CT(f1,a- f1,i+ f3,i- f3,a) - 1000(10-pHa -10-pHi +10pHi-pKw-10pHa-pKw)
75
Alkalinity II
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
121110987654
pH
Distribution of CARBO as a function of pH
CARBOnic biCARBOnate CARBOnate
Fractions.EPSF
- Definition: The number of mEq of acid which must be added to a liter of water to bring pH to 4.3 (IOW, to convert most carbonate and bicarbonate to carbonic). Multiply by 50 for ppm as CaCO3.
Example sample pHi
Where you goduring titration
Where you’dLike to be inMash tun
- A rough indication of the amount of acid needed in the mash per L water
- Measured by titration (addition of small amounts of acid until pH 4.3 is reached and reporting total used)
76
Alkalinity - Procedure
• Add an indicator (e.g. methyl orange or bromcresol green-methyl red) or a pH electrode to 100 mL sample
• Using a buret (conventional, digital, automatic, eyedropper, syringe…) add 0.1N (.1 mEq/L) acid (usually sulfuric) to sample until indicator turns color or pH 4.3 is reached– Other endpoint pH values can be used
• Report total number of mL acid used and endpoint pH– Multiply by 50 for ppm as CaCO3.
• Kits available: Hach AL-AP $36.79 (100 tests)– Phenolphthalein (8.3) and Bromcresol Green-Methyl Red (4.3)
indicators, sulfuric acid, measuring tube and bottle
77
Alkalinity Titration using pH Meter (Indicator also present)
Sulfuric acid cartridge Digital Titrator:Plunger, lead screw,
counter
pH electrode
pH Meter
Dip Tube
78
Total Hardness (Ca++ + Mg++)
• Certain dyes (e.g. Eriochrome Black) are one color (red) in the presence of Ca++ or Mg++ and another color (blue) in their absence.
• Add such a dye to 100 mL of sample with buffer to set pH for sharp end point
• Titrate with a standardized strength chelating agent (EDTA) until the sample changes from red to blue.
• Report the number of mL chelant used (it has been calibrated to a convenient number of mEq or ppm or grains or dH (German degrees) etc. hardness per mL)
• This gives the total hardness (sum Ca + Mg)• Kits available: Hach HA-71A $48.25 (100 tests)
– Test tube/bottle, EDTA, Indicator, buffer, 20 ppm res.
79
Calcium Hardness
• Remove Mg++ from water by raising pH (add suitable buffer)– Mg++ + 2(OH)- --> Mg(OH)2 (insoluble gel)
• Add dye and titrate with EDTA as before. This gives calcium hardness
• Subtract from total hardness to get magnesium hardness• Kits available: Hach HA-4P Total and Calcium Hardness
$65.05 (100 tests) 20 ppm as CaCO3 resolution– Test tube and bottle, 2 indicators, 2 buffers, EDTA– Doubling amount of sample halves resolution (to 10 ppm) and
halves number of tests per kit (to 50).
80
Hardness - Colorimetric• Add dye to sample• Divide into three portions• Chelate Ca++ and Mg++ from first (excess EDTA)• Chelate Ca++ only from second (excess EGTA)• Do nothing to third.• Zero spectrophotometer with first - read second. Color depth
difference is proportional to Mg++
• Zero specrophotometer with second - read third. Color difference is porportional to Ca++
• Add the two values for total hardness.• No simple kits available - requires photometer or
spectrophotometer.
81
Chloride• Titration (kits available)
– Diphenyl Carbazone forms a light pink complex with Hg++ (mercuric) ions– Add DPC to sample, titrate with calibrated mercuric nitrate.– Precipitate of HgCl2 forms.– When all Cl- has precipitated any additional Hg++ forms colored complex with
diphenyl carbazone.– Amount of Hg(NO3)2 used to obtain color is proportional to amount of chloride in
sample
• Colorimetry (uses photometer)– Add Mercuric Thiocyanate
• Hg(SCN)2 + Cl- ---> HgCl2 + 2SCN-
– Add ferric ion solution• 3SCN- + Fe+++ ---> Fe(SCN)3 (red orange)
– Measure depth of color formed with photometer.
• Note: Nasty mercury salts used in both these - Hg waste
82
Sulfate
• Barium sulfate is insoluble, Barium chloride is soluble.
• Add barium chloride to sample. Barium coalesces with sulfate to form insoluble BaSO4
– Special agents in test reagent keep this in suspension
• Read turbidity in turbidimeter or spectrophotometer calibrated with standard solutions.
• No kits available - requires turbidimeter or photometer.
83
Sodium• No practical chemical method• Atomic Absorption/Atomic Emission Spectrophotometry
– Sample is vaporized into flame. Optical absorption (or emission) at 589.6 nm is measured.
• Ion Selective Electrode (ISE)– Similar to pH electrode except that its glass responds to log{Na+} rather
than log{H+}– Expensive (hundreds of $)– Electrical response to calibrated standards is recorded (similar to pH).– Electrical response to sample is recorded
• Electrode is very slow to respond (especially at low concentrations) so automatic (e.g. strip chart) recording is preferred
– Sample response is interpolated into calibration “curve”• Some meters have the math built in
84
Sodium - Multiple Additions
• mV = U1 + Unlog{Na+}– U1 = response to 1 mg/L (unknown)– Un = response change per decade (only approximately known)– {Na+} = sample sodium concentration (what we want to know)
• Place electrode in known volume, v0, of sample and record response• Add “spikes” i.e. known volumes v1, v2… mL of sodium standard solution
of known strength S mg/mL. Then…• mV0 = Unlog(v0{Na+}0) + U1
• mV1 = Unlog(v0 {Na+}0 + S(v1)/(v0 + v1)) + U1
• mV2 = Unlog(v0 {Na+}0 + S(v1 + v2 )/(v0 + v1 + v2 )) + U1 • 3 measurements are sufficient (though more are better) to allow estimation of
{Na+}0, Un, and U1
• Math is not basic (iterative non linear mmse estimation) but easily handled in a laptop
– Excel Solver can do it!
85
-130
-125
-120
-115
-110
-105
-100
-95
Electrode Response, mV
8:30 AM9/23/08
9:00 AM 9:30 AM 10:00 AM
Time
25
24
23
22
21
Temperature, °C
Fit from here...
...to here-111.6mV
-110.99 ± 0.028 mV
Sodium Electrode Response50 mL Sample; 1 ml Spikes of 100 mg/mL
Response Temperature Exponential fit to response
Sodium ISE Recording Example
86
Analysis of Assymptotic mV Readings from Previous Slide
Slope = 48.4336, Intercept = -148.0979 mV, Concentration = 5.8632 ± 0.0255 mg/L; rmse = 0.1015 mV after 88 iterations. Un DOP = 4.74 mV/decade/mV; U0 DOP = 7.57 mV/mV; Concentration DOP = 4.48 mg/L/mV
-110
-108
-106
-104
-102
-100
-98
-96
Electrode Response, mV
6 7 8 910
Calculated Concentration, mg/L
Calculated and Measured Electrode Response Mesured ResponseCalculated Response based on
Estimated Parameters
0.15
0.10
0.05
0.00
Measured - Calculated, mV
5453525150
Total Volume, mL
Differences Between Calculated ElectrodeResponse Based on MMSE Estimates ofSlope, intercept and Initial Concentrationand Measured Response
87
Chlorine/Chloramine
• N,N-diethyl-p-phenylenediamine (DPD) added to sample
• Magenta Würster Dye formed if free chlorine is present
• Depth of color measured on photometer or judged relative to printed color patches, color wheels etc.
• Where chloramine is present it is converted to free chlorine first - total reading
• Difference RE free chlorine measurement is chloramine
• Kit: Hach CN-66 $45.29 (50 tests total; 50 free)- 0.1 ppm resolution– DPD, color wheel, 2 test tubes, test fixture.
88
Other Ions• There are tests for dozens of other ions
– Fe(II), Fe(III), Cu, Mn, Zn, NO2, NO3, K, Al, SiO2, NH3… all based on similar principals
– Kits are available for many (www.hach.com)
• Most of these are not important in brewing unless well in excess of typical values– i.e. in excess of EPA secondary limits
• Water tastes bad.
– If in excess of primary limit, don’t drink it or brew with it– Fe, Cu, Zn in excess may indicate corrosion
• Zn in particular may indicate leaching from brass in well fittings with potential that lead is being extracted as well
– Brass containing lead now prohibited in wells
89
Summary of Measurement Techniques
• Titration– Addition of reagent of calibrated strength until an end point (color
change, particular pH…) is reached
• Color development; color depth measurement– By visual comparison to printed chart, color wheel etc.– By use of photometer of spectrophotometer
• Gravimetry– A precipitate is formed, separated and weighed– A precipitate is formed and kept in suspension. Its ability to scatter light
is mesured by a nephelometer or spectrophotometer
• Electrochemistry– An electrode which responds to the concentration of a particular species
of ion is placed in the sample.
Practical Considerations
• Only the simplest tests (alkalinity, hardness, chorine) can be done without a lot of trouble and expense– Of limited but sufficient accuracy for brewing
• More accurate measurements, as with pH, require calibration with standards– Chemistries age. Old chemistries can be used past
expiration dates but standards must be employed– Much more involved than tolerability unless this is part of
the hobby (or commercial operation)
90
91
Part VIISynthesizing Water With Desired
Profile
92
Where Do I Get Profiles?• From textbooks, friends, articles, the internet, the ones
on the handout CD ROM– Caution - not all profiles are physically realizeable.
• Reporting, measurement, interpretation errors• Reporting of average values
– Simple check: add up all ion concentrations, specify a pH and calculate net electronic charge
• Must be close to 0 (imbalance of a few %)• Easily done with spreadsheet on CD ROM • Same as for evaluating quality of water reports
• You can’t get a good approximation to an unrealizeable profile!
93
Target Profile:Burton on Trent
Target WaterpH 6.60 4.300 End Point pHTemp + for C, - for F 20.0 20.0 Temp, CTemp K 293.20 293.20pK1 6.38 6.38pK2 10.38 10.38pKw 14.16 14.16A 0.714r1 1.65 0.01r2 0.00 0.00f1 = 1/d 0.38 0.99 Bicarb. @ pHa [H+] @ pHa Differencef2 0.62 0.01 0.048 0.050 -0.002f3 0.00 0.00f1 + f2 + f3 1.00 1.00No carb alkalinity 0.0499
Alk, + as CaCO3, - mEq/L 182.30Ca, + as CaCO3, - as mg/L -352.00Mg, + as CaCO3 - as mg/L -24.00Alk, mEq/K 3.65 Gram Eq. Wt Cations Anions
352 <-- mg/L Ca mEq/L--> 17.56 20.04 17.565 Ca24 <-- mg/L Mg mEq/L--> 1.97 12.15 1.975 Mg
Rough Carbo 5.84717Rough Carbonic 96.96 0.000Rough Bicarbonate 222.22 61.03 Rough Carbonate 0.06 30.02 Total Carbo, mg/L 5.82420H2CO3, mg/L 96.58HCO3-,mg/L 221.45 3.629 BicarbonateCO3--,mg/L 0.04 0.001H+ 0.00 0.000(OH)- 0.00 0.000Sulfate. mg/L 820.00 48.04 17.071 SulfateChloride, mg/L 16.00 35.45 0.451 ChlorideNitrate, mg/L 18.00 62.00 0.290 NitrateNitrite, mg/L 0.00 47.00 0.000 NitriteSodium, mg/L 44.00 22.99 1.914 SodiumPotassium, mg/L 0.00 39.10 0.000 PotassiumFe(II), mg/L 0.00 27.92 0.000 Fe(II), mg/LFe(III), mg/L 0.00 18.62 0.000 Fe(III), mg/L
Free Ammonia, mg/L 0.00 32.01 0.000 23173.174
Charges 21.454 21.442Imbal 0.012Imbal % 0.03%
Alkalinity 182.30Ca Hardness, as CaCO3 878.24Mg Hardness, as CaCO3 98.75
Total Hardness, as CaCO3 976.99
Residual Alkalinity -82.73 ppm as CaCO3Residual Alkalinity -1.65 mEq/L pH Shift RE Distilled Water -0.14
Ionic Strength 39.76 37.94
pfm 0.1102 0.1083
94
Base Water
• Deionized (DI) water (distilled, ion exchanged but not by home water softener!) represents “blank piece of paper”– RO water is a decent approximation to DI
• Other water: can increase an ion concentration easily but not decrease it – Dilution with DI/RO water– Bicarbonate can be removed to some extent
• Takes calcium and magnesium with it.
• Modern municipal supplies generally represent a decent starting point
95
Available WaterpH 6.00 4.300 End Point pHTemp + for C, - for F 20.0 20.0 Temp, CTemp K 293.20 293.20pK1 6.38 6.38pK2 10.38 10.38pKw 14.16 14.16A 0.714r1 0.42 0.01r2 0.00 0.00f1 = 1/d 0.71 0.99 Bicarb. @ pHa [H+] @ pHa Differencef2 0.29 0.01 0.034 0.050 -0.016f3 0.0000 0.0000f1 + f2 + f3 1.00 1.00No carb alkalinity 0.0491
Alk, + as CaCO3, - mEq/L 62.00Ca, + as CaCO3, - as mg/L 71.00Mg, + as CaCO3 - as mg/L 48.00Alk, mEq/K 1.24000 Gram Eq. Wt Cations Anions<-- mg/L Ca mEq/L--> 1.42 20.04 1.420<-- mg/L Mg mEq/L--> 0.96 12.15 0.960Rough Carbo 4.17535Rough Carbonic 129.81 0.000Rough Bicarbonate 74.73 61.03 Rough Carbonate 0.01 30.02 Total Carbo, mMol/L 4.16054H2CO3, mg/L 129.35HCO3-,mg/L 74.50 1.221CO3--,mg/L 0.00 0.000H+ 0.00 0.001(OH)- 0.00 0.000Sulfate. mg/L 20.40 48.04 0.425Chloride, mg/L 7.00 35.45 0.197Nitrate, mg/L 0.00 62.00 0.000Nitrite, mg/L 0.00 47.00 0.000Sodium, mg/L 0.00 22.99 0.000 Potassium, mg/L 0.00 39.10 0.000Fe(II), mg/L 0.00 27.92 0.000Fe(III), mg/L 0.00 18.62 0.000
Free Ammonia, mg/L 0.00 32.01 0.000 23173.174
Charges 2.381 1.843Imbal 0.538Imbal % 12.74%
Alkalinity 62.00Ca Hardness, as CaCO3 71.00Mg Hardness, as CaCO3 48.00
Total Hardness, as CaCO3 119.00
Residual Alkalinity 34.86 ppm as CaCO3Residual Alkalinity 0.70 mEq/L pH Shift RE Distilled Water 0.06
Ionic Strength, non carbo 2.90 Ionic Strength, carbo 0.61224Total Ionic Strength 3.52pfm 0.0392 0.0358910 pfm, no carbo
Source WaterMcLean Well
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Approach to Synthesis• Simply add anything that is deficient!
– Catch: You must add salts. Ratio of calcium to chloride in CaCl2 is fixed! (100mg Ca:35mg Cl)
– Nevertheless you can do quite well using a few common salts• NaCl, MgSO4.7H20, NaHCO3 Source - grocery or drugstore
– Table salt (don’t use iodized!), epsom salts, baking soda • CaSO4.2H20, CaCO3, CaCl2.2H2O Source homebrew supply shop
– Gypsum, (precipitated) chalk, calcium chloride
– If using carbonate, bicarbonate or changing alkalinity you will need acid• This can be CO2• Sulfuric or Hydrochloric (not recommended: FCC, USP, safety)
– Math is nettlesome: successive approximations by manipulation of salt addition amounts until combined error in ion concentrations is small
– Excel Solver to the rescue!• Set up the problem and let the Solver do the work.
FCC = Food Chemicals Codex i.e. approved for use in food for human consumptionUSP = United States Pharmacopoeia i.e. approved for use in drugs for humans
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Adding an Ion from a Salt• Gypsum is CaSO4.2H2O GMW 172.14• Each millimole of 172.14 mg contains 40 mg of Ca++ and 98 mg of
SO4--
• To add, for example, 60 mg/L Ca++ would require 60/40 = 1.5 mMol = 258.2 mg gypsum for each litre treated– And you are also adding 1.5*98 = 147 mg/L SO4
-- like it or not.
• To add 250 mg/L sulfate use 250/98 = 2.55 mMol = 440 mg/L– And you are also adding 2.55*40 = 102 mg/L Ca++ like it or not.
• Spreadsheet does all this math for you.• Compromise necessary because of fixed relative amounts of ions in
salts• If target is reasonable, spreadsheet can do a fairly good job and it’s a
lot easier than doing the math yourself
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Salts/Acids CaCl2.2H20 NaCl CaSO4.2H20 MgSO4.7H20 CaCO3 NaHCO3 CO2 HCl H2SO4Addition, mg/L 0.00 14.95 1386.65 75.96 55.35 136.41 0.00 0.00 0.00
Total, mg/L
Calcium, mMol/L 0.00 8.05 0.00 350.6156Magnesium, mMol/L 0.31 23.9935
Total Carbo mMol/L 0.55 1.62 0.00 6.3375Carbonic, mMol/L 0.21 0.61 0.00 105.0914Bicarb. mMol/L 0.34 1.01 0.00 240.9737Carbonate, mMol/L 0.00 0.00 0.00 0.0398Proton excess mEq/L -0.76 -0.61 0.00 0 0 0.0000
Sulfate, mMol/L 8.05 0.31 0 823.1663Chloride, mMol/L 0.00 0.26 0 16.0704Nitrate, mMol/L 0.0000Nitrite, mMol/L 0.0000Sodium, mMol/L 0.26 1.62 43.2068Potassium, mMol/L 0.0000Fe(II), mg/L 0.0000Fe(III), mg/L 0.0000
Free Ammonia, mg/L 0.0000
Ionic Strength SYNTHESISExtra ~ pH shift 0.6865 Allkalinity 198.0818Carbonic~ addition 0.6783 Ca Hardness, as CaCO3 874.7895Extra non carbo 34.5162 Mg Hardness, as CaCO3 98.7185Synthesized carbo 1.9770Synthesized non carbo 37.4196 Total Hardness 973.5080Synthesized total 39.3966Synthesized pfm w/o carbo 0.1077 Residual Alkalinity -65.9607Synthesized pfm w/ carbo 0.1098 Residual Alkalinity -1.3192
pH Shift RE Distilled Water -0.11
Vol. + for Gal - for L 54Litres 204.4116
Grams of salt or acid 0.000 3.056 283.448 15.526 11.314 27.884 0.000 0.000 0.000Amount in other units 0.00 0.01 0.62 0.03 0.02 0.06 0.00 0.00 0.00Units Pounds ^ Pounds ^ Pounds ^ Pounds ^ Pounds ^ Pounds ^ Pounds ^ mL 23 Be' mL 96% 1.856 g/LAmount in Oz. 0.00 0.11 9.99 0.55 0.40 0.98 0.00 Salts/Acids CaCl2.2H20 NaCl CaSO4.2H20 MgSO4.7H20 CaCO3 NaHCO3 CO2 HCl H2SO4
pRatio Weights Errors, % Errors, mg/L-0.002 1 -0.4% -1.3843520.000 1 0.0% -0.0064754
0.037 1 8.8% -19.52
0.002 1 0.4% 3.170.002 1 0.4% 0.070.000 0 0.0% -18.000.000 0 0.0% 0.00
-0.008 1 -1.8% -0.790.000 0 0.0% 0.000.000 0.0% 0.000.000 0.0% 0.000.000 0.0% 0.000.0000.000 0 0.0% 0.00
MSE Wt'd MSE MSE,%0.001 0.00142 0.3%0.000
H+ Imbal.
Synthesis Portion of Spreadsheet
Specify salt additions hereResulting ion concentrations
Relative importancein computing error
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Water Worksheet Summarized• Three parts (two identical)
– These two accept your inputs of pH, alkalinity(as CaCO3 or mEq), hardness (as CaCO3 or mg/L), other ion content, temperature (°F or °C)
– Compute balance, residual alkalinity, ionic strength, carbo species ratios and fractions
• Must have balanced target; should have balanced source
– One on left is for source water– One on right is for target water profile – Middle part is for synthesis of target from source
• Manually indicate the amount of each salt or acid you want to try• Check errors (differences between desired and realized)• Adjust until “close enough for government work”• Better still: Let Excel Solver do this for you
• Detailed instructions on Sheet 2 of spreadsheet
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More on Acid Requirements
• If you use NaHCO3 and/or CaCO3 in a synthesis pH will most probably shift and CaCO3 probably won’t dissolve– Acid is required to set pH to desired value and dissolve CaCO3
– If you have used these to match alkalinity and then intend to decarbonate, save yourself the trouble - synthesize for stylistic ions only
• Much will probably precipitate when water is heated in HLT
• I do not recommend the use of strong mineral acids for safety reasons• That leaves CO2. Add salts and stir. Water will be cloudy as CaCO3
will be in suspension• Bubble CO2 through water until it clears and pH is about right - this
may take some time (hours).– Pressure helps dissolve CO2 - put salts in Corny keg, pressurize, agitate– Target pH not that critical. Will go where it wants to in HLT, mashtun
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Part VITreatment
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At Water Treatment Plant• Depending on source, strong oxidants may be used to “burn” off
flavors, aromas– Chlorine, potassium permanganate
• Mix with salt of trivalent metal (Fe, Al)– Forms hydroxide gel which is allowed to settle– Drags down particles (silt, bacteria, viruses) with it
• Decant, filter (may include active carbon)…• Adjust alkalinity, hardness, pH
– Same way we do! Add acids, lime, salts to desired profile– Mostly for protection of distribution system– Set to near saturation pH (small amounts of lime precipitated)
• Inject chlorine and/or ammonia and/or ozone• Send to distribution system
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At Home - Well• Wound filters remove particulates• If iron is present Aeration/sand filter (or greensand filter) • If water is acidic (subterranean CO2) run through limestone (neutralizer).
Prevents corrosion; increases hardness and alkalinity.• Softener - Don’t use for brewing water!
– Ion exchange resin loaded with Na+ (sometimes K+)– Replaces Ca++, Mg++ with Na+ (sometimes K+)– Backwash with brine, NaCl (or KCl) recharges medium. Replaces Na+ (or
K+) while Ca++, Mg++ go down drain.• Removes beneficial hardness and replaces with useless Na+ (or K+)
• Reverse Osmosis (RO) units force water through membrane with small pores removing most ions (95-99%)
• Activated carbon filter: removes organics, mustiness…• Anion/Cation ion echanger (see next slide)
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At Home - City Water• Wound filters remove particulates• Softener - Don’t use for brewing water!• Activated carbon filter: removes chlorine, chloramine,
organics– Required if RO unit is installed - HOCl, H2NCl poison membrane – Available as whole house or at sink installations
• Reverse Osmosis (RO) units force water through membrane with small pores removing most ions (95-99%)
• Cation/Anion exchanger:– Swaps H+ for all cations, (OH)- for all anions. Result: DI water.– Brita filters in this class (also contain silver as Ag+ is bacteriostatic)
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Decarbonation/Softening• Goal is decarbonation (reduction of alkalinity). Softening is the price
that usually must be paid.– Ca++ + 2HCO3
- -----> CO2 + CaCO3 + H2O• Calcium is removed but only to extent of bicarbonate e.g water with alkalinity of 100
ppm as CaCO3 and hardness of 200 ppm as CaCO3 precipitates all (theoretically) its bicarbonate and half its calcium
– Decarbonation limit practially about 50 ppm as CaCO3
• Calcium so precipitated is called temporary hardness• Remaining calcium is called permanent hardness
– Ca(OH)2 + Ca++ + 2HCO3- ----> 2H2O + 2CaCO3
• This is actually neutralization of the acid HCO3- with the base Ca(OH)2 which suggests
procedure (next slide)• Decarbonation limit practially about 50 ppm as CaCO3
– Ca++ + 2HCO3- + 2HCl ----> 2CO2 + Ca++ + 2Cl- + 2H2O
• No softening: temporary (carbonate hardness) converted to permanent (non carbonate hardness) - no decarbonation limit
heat
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Lime Decarbonation• Calculate amount of lime required
– CaO (quick lime) + H2O --> Ca(OH)2 (slaked lime) + heat • Pickling lime is slaked. Available in canning section of supermarket
– 1 mMol of slaked lime (74 mg) treats 2 mEq bicarbonate (122 mg or 100 ppm as CaCO3 alkalinity)
• Ca(OH)2 + Ca++ + 2HCO3- ----> 2H2O + 2CaCO3
• All added calcium precipitates. No hardness increase (theoretically)
– DeClerck recommends treating trial batches with this amount and ±10%. Then use dose that gave best results
• Add to 2/3 the water to be treated– Wait for Mg(OH)2 to precipitate and decant if
• Called (split treatment). Only necessary if Mg is to be reduced• Excess lime with only 2/3 water raises pH to where Mg(OH)2 forms
– Titrate back to pH 8 or so with remaining volume– Allow to settle and decant
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Iron• Fe++ (clearwater iron) is soluble• Fe(OH)3 is insoluble (ugly brown) gel• Approach to treatment is, thus, to oxidize any Fe++ to Fe+++, at higher
pH Fe(OH)3 gel forms. Filter gel– 4Fe++ + 2H2O + O2 +8(OH)- --> 4Fe(OH)3 (gel)– Gel gets caught by sand. Backwash to dispose– Aeration supplies oxygen and sweeps CO2 raising pH, increasing (OH)-
• Aeration by spraying, sparging with air, pouring back and forth then pouring through clean sand works
• Commercial units inject air and then pass through sand bed - similar construction as neutralizers, softeners
• Manganese greensand oxidizes Fe++ (and Mn++ and S-) and traps gels– It’s Mn(IV) that does job. Recharge with Mn (VII) i.e. KMnO4
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Chlorine/Chloramine• These must be removed from brewing water
– Form chlorphenolics with plastic, bandaid flavor at ppb level.
• Water treatment plants have bubbled chlorine gas into product for years - significant public health factor– H2O + Cl2 <--> H+ + Cl- + HOCl
• Uncharged hypochlorous acid slips through bacterial cell wall disabling key enzymes - strong oxidizing agent
– Standing, boiling, sparging reverses reaction removing chlorine• More recently, ammonia is added after chlorination
– NH3 + HOCl --> H2O + H2NCl : Monochloramine• Less likely to produce Trihalomethanes (THMs)• More stable (persistent) in distribution system• More persistent when you try to remove it
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Removing Chloramine
• Boiling is effective but it takes an hour or more• Granulated activated charcoal (GAC) filters are
effective but make sure contact time is long enough– Limit flow rate
– If you can smell it, it “broke through”
• Simplest treatment: 1 Campden Tablet for 20 gal.– Crush and suspend in a small amount of water, stir in.
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Part -XXComparison Beer
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“…and why was Burton Built on Trent?”
• “…well water drawn from the evaporite-rich Permo-Triassic sandstones outside of town”
• It must make good beer because water doesn’t taste very good– High sulfate accentuates hop character, stabilizes beer biologically (IPA)
• I have 7 profiles for Burton (all on handout CD). One which balances at pH 6.6 (i.e. a “reasonable” one) and shows:– Alkalinity: 182 ppm as CaCO3
– Calcium Hardness: 878 ppm as CaCO3
– Mg Hardness: 99 ppm as CaCO3
– Residual Alkalinity - 83 ppm as CaCO3 (pH Shift -0.17)– Sulfate: 820 mg/L– Chloride: 16 mg/L– Sodium: 44 mg/L
• This one was implemented with well water, baking soda, table salt (not iodized), epsom salts, gypsum, precipitated chalk and CO2.
• 1.5 bbl batch brewed using Maris Otter, some Munich, 1058 London ale, Sterling, US Kent Goldings and EKS - 12.7°P
• Same beer brewed with untreated well water
A. E. Houseman, Shropshire Lad
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Brewing
200
180
160
140
120
100
80
Temperature, °F
12:30 PM9/8/08
3:00 PM 5:30 PM 8:00 PM 10:30 PM
Time, Z
Batch 126a (Burton - done first)and 126b (normal water) ales
Mashtun 1 Mashtun 2
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Fermentation64
62
60
58
56
54
52
50
48
46
44
42
40
38
36
34
Temperature, °F
9/9/08 9/11/08 9/13/08 9/15/08 9/17/08 9/19/08 9/21/08
Time, Z
Fermentation History: Ale Batches 126a and 126b !26b - Normal Water 126a - Burtonized Water
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Tasting
• Look for differences in– Esters (aroma & flavor): Fruit, berry…– Yeast aroma: Bready?– Hops: (aroma & flavor):bitterness, sharpness, coarseness,
fruity– Sweetness– Mouthfeel: viscosity, mellowness, astringency/dryness,
rough/smooth, bite
• Is one beer “better” than the other?– If so and it’s the Burtonized one is it enough better that
it’s worth the trouble?
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Further Reading
• Basic inorganic chemistry text
• The articles on the handout CD
• Palmer, John, How to Brew 978-0-937381-88-5
• Hardwick, W. A. (Ed.) Handbook of Brewing 0-8247-8908-3
• De Clerck, J. A Textbook of Brewing (no ISBN! – get it from Siebel)
• Noonan, G, New Brewing Lager Beer 0-937381-46-2
• Foster, Terry, Pale Ale 2nd Edition 0-937381-69-1
• Eaton, et al. Eds. Standard Methods for the Examination of Water and Wastewater
