Total hardness in tap water | Autotitrator COM-A19 - JM Science

HIRANUMA APPLICATION DATA Automatic Titrator Data No. D2 Nov. 14,2018
Environment Total hardness in tap water

1. Abstract

 Hardness in water is total amount of calcium and magnesium ion in water converted to mg/L of comparable calcium carbonate. “Hardness” has the following types:

 (1) Total hardness     Total amount of calcium and magnesium ions
 (2) Calcium hardness    Calcium ion
 (3) Magnesium hardness (Total hardness) – (Calcium hardness)
 (4) Non-carbonate hardness (Permanent hardness)
 (5) Carbonate hardness (Temporary hardness)

 These are stipulated in some applicable standard such as Standard Methods for the Examination of Water, Standard Methods of Analysis for Hygienic Chemists, and JIS K0101 Testing methods for industrial water etc.
 This report introduces an example for determination of total hardness in tap water with photometric titration method using EDTA standard solution according to the Standard Methods for the Examination of Water.
 Take 100 mL of sample and add 1 mL of 0.01 mol/L magnesium chloride, 2 mL ammonia buffer, and 0.2 mL of EBT indicator. Titrate with 0.01 mol/L EDTA standard solution (red →blue color). Perform the same procedure for 100 mL of DI water instead of sample as blank measurement.

CaCO₃ + Na₂EDTA → Ca-EDTA + Na₂CO₃  
MgCO₃ + Na₂EDTA → Mg-EDTA + Na₂CO₃  

2. Configuration of instruments and Reagents

(1) Configuration of instruments
  Main unit : Hiranuma Automatic Titrator COM Series
(M type photometric unit for photometric titration with 650 nm optical filter)
(2) Reagents    
    Titrant : 0.01 mol/L EDTA standard solution
    Additive solution : 0.01 ml/L Magnesium chloride solution
  Buffer solution : Ammonium chloride-ammonia buffer solution (pH 10)
Dissolve 6.75 g of ammonium chloride in 30 mL of DI water, add 57 mL of ammonia solution, and dilute to 100 mL with DI water.
    Indicator : EBT Indicator
Dissolve 0.5 g of eriochrome black T and 4.5 g of hydroxylammonium chloride in 100 mL of ethanol (95 % [v/v]).

3. Measurement procedure

(1) Dispense 100 mL of sample into a 200 mL beaker with volumetric pipette.
(2) Add 1 mL of 0.01 mol/L magnesium chloride solution with volumetric pipette.
(3) Add 2 mL of ammonia buffer.
(4) Add 0.2 mL of EBT indicator.
(5) Immerse photometric probe and start titration with 0.01 mol/L EDTA standard solution.
(6) Perform the same procedure for 100 mL of DI water as blank measurement

4. Measurement conditions and results

Examples of titration conditions

Measurement of blank
Total hardness in tap water
Measurement of sample

Total hardness in tap water

Measurement results

Measurement of blank
Number of
measurement
Size
(mL)
Titrant
volume(mL)
1 1.041
2 1.041
3 1.038
Statistic
calculation
Avg. 1.040 mL
SD 0.0017 mL
RSD 0.17 %
Example of titration curves

Sample Measurement results
Number of
measurement
Size
(mL)
Titrant
volume(mL)
Total hardness
(ppm)
1 100 6.718 56.837
2 100 6.745 57.107
3 100 6.719 56.847
Statistic
calculation
Avg. 56.9 ppm
SD 0.153 ppm
RSD 0.27 %

 

 Example of titration curves

5. Note

(1) Measurement
 The total hardness in tap water can accurately be determined by photometric titration method with EBT indicator using photometric probe.
(2) End point detection
 “Method” on the condition parameter is set to “B cross” because the point where indicator color change is completed is detected as endpoint. When the concentration of total hardness is relatively high and much titrant volume is required, “C.P. mL” function is useful. Titrant can be added at once by setting “C.P. mL” to a few mL smaller than titrant volume at the endpoint, it can reduce measurement time.

 

Keywords: Tap water, Total hardness, Photometric titration, EDTA standard solution



*Some measurement would not be possible depending on optional configuration of system.

EnvironmentHiranuma aquacounter autotitrator com-a19

Featured Instruments

Aquacounter Potentiometric Titrator COM-A19 | HiranumaAquacounter Potentiometric Titrator COM-A19 | Hiranuma
Hiranuma Aquacounter Potentiometric Titrator COM-A19 | Hiranuma
Sale price$11,490.00 USD Regular price$12,490.00 USD

Featured Titrators

View all
Aquacounter AQ-300 Coulometric Karl Fischer Titrator | Hiranuma
Hiranuma Aquacounter AQ-300 Coulometric Karl Fischer Titrator | Hiranuma
Sale price$5,500.00 USD Regular price$6,990.00 USD
Aquacounter Volumetric Karl Fischer Titrator MOIVO-A19 | Hiranuma
Hiranuma Aquacounter Volumetric Karl Fischer Titrator MOIVO-A19 | Hiranuma
Sale price$11,990.00 USD Regular price$13,990.00 USD
Aquacounter Coulometric Karl Fischer Titrator MOICO-A19 | Hiranuma
Hiranuma Aquacounter Coulometric Karl Fischer Titrator MOICO-A19 | Hiranuma
Sale price$10,990.00 USD Regular price$12,490.00 USD
Aquacounter Potentiometric Titrator COM-A19 | HiranumaAquacounter Potentiometric Titrator COM-A19 | Hiranuma
Hiranuma Aquacounter Potentiometric Titrator COM-A19 | Hiranuma
Sale price$11,490.00 USD Regular price$12,490.00 USD
Aquacounter AQV-300 Volumetric Karl Fischer Titrator | Hiranuma - JM Science
Hiranuma Aquacounter AQV-300 Volumetric Karl Fischer Titrator | Hiranuma
Sale price$5,500.00 USD Regular price$6,990.00 USD