Point of reflection – reconvene

Welcome back. So what were your thoughts? 

We know that Total Hardness is measured as mg/L of CaCO3. We also know that we can calculate the Total Hardness as CaCO3 by using one of two equations. Let us go through both options:

Option 1:

Total Hardness as Error converting from MathML to accessible text.

Total Hardness as Error converting from MathML to accessible text.

                                             Error converting from MathML to accessible text.

                                             = 95.5 mg/L

Option 2: Total Hardness as CaCO3 = (2.5 x Ca2+) + (4.12 x Mg2+)

                                                                = (2.5 x 25) + (4.12 x 8)

                                                                = (62.5) + (32.96)

                                                                = 95.5 mg/L

The calcium hardness can also be obtained by titrating 100 mL of the water with a 0.02M solution of EDTA, buffered with a strong alkaline solution, such as sodium hydroxide (NaOH) to an indicator end point using Patton and Reeder’s Reagent indicator. Calcium hardness is expressed as CaCO3, where 1 mL of EDTA solution is equivalent to 1 mg of calcium. 

The magnesium hardness is the difference between the total hardness and the calcium hardness.

Therefore, at the end of the calculation or titrations, we get a value for total hardness as CaCO3. However, what does that mean? What levels of Total Hardness constitute hard or soft water? 

According to the European Brewery Convention Manual of good practice: ‘Water in Brewing’, the classification of water hardness is as follows:

Table: Classification of water hardness

CaCO3 (mg/L)

Classification

0-37.5

Very soft

37.5-87.5

Soft

87.5-175

Medium hard

175-375

Hard

> 375

Very hard

Point of reflection: At the start of this lesson, we saw a table of the water quality parameters from around the world. Using this table, define the hardness of the water for each of the locations.

Beer Type

Burton 

London 

Dublin 

Munich 

Pilsen 

Melbourne 

Sodium

30

24

12

1

3

4.5

Magnesium

62

4

4

19

1

0.8

Calcium

268

90

119

80

7

1.3

Chloride

36

18

150

1

5

6.5

Sulphate

638

58

15

5

6

0.9

Carbonate

141

123

20

164

9

3.6

Nitrate

31

3

-

3

-

0.2

Total Dissolved Solids

1226

320

320

273

31

25

Give yourself 5-10 min to think about this, and then click ‘Next’ to continue with this lesson.

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