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  • ASTM D5128-14

ASTM D5128-14

Standard Test Method for On-Line pH Measurement of Water of Low Conductivity

ASTM International, 01/01/2014

Publisher: ASTM

File Format: PDF

$38.00$76.00


Published:01/01/2014

Pages:11

File Size:1 file , 330 KB

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1.1 This test method covers the precise on-line determination of pH in water samples of conductivity lower than 100 μS/cm (see Table 1 and Table 2) over the pH range of 3 to 11 (see Fig. 1), under field operating conditions. pH measurements of water of low conductivity are problematic for conventional pH electrodes, methods, and related measurement apparatus.

TABLE 1 Calculated Conductivity and pH Values at 25°C of Low Concentrations of NaOH in Pure Water A
Note 1-This table tabulates the theoretical conductivity and pH values of low levels of NaOH in pure water as calculated from available thermodynamic data.
Note 2-To illustrate the high sensitivity of the sample pH at these low concentrations to contaminants, the last column lists errors that would result if the sample were contaminated with an additional 1 mg/L through sample or equipment handling errors.

Sample
Concentration,
mg/L

Sample
Conductivity,
μS/cm

Sample
pH

Δ pH Error from Additional 1 mg/L NaOH Contaminate

0.001

 0.055

 7.05

Δ 2.35

0.010

 0.082

 7.45

Δ 1.95

0.100

 0.625

 8.40

Δ 1.03

1.0

 6.229

 9.40

Δ 0.30

8.0

49.830

10.30

Δ 0.05
A Data courtesy of Ref (1).B This data developed from algorithms originally published in Ref (2).
B The boldface numbers in parentheses refer to a list of references at the end of this standard.
TABLE 2 Calculated Conductivity and pH Values at 25°C of Low Concentrations of HCl in Pure Water A
Note 1-This table tabulates the theoretical conductivity and pH values of low levels of HCl in pure water as calculated from available thermodynamic data
Note 2-To illustrate the high sensitivity of the sample pH at these low concentrations to contaminants, the last column lists errors that would result if the sample were contaminated with an additional 1 mg/L through sample or equipment handling errors.

Sample
Concentration,
mg/L

Sample
Conductivity,
μS/cm

Sample
pH

Δ pH Error from Additional 1 mg/L HCl Contaminate

0.001

 0.060

6.94

Δ2.38

0.010

 0.134

6.51

Δ 1.95

0.100

 1.166

5.56

Δ 1.03

1.0

11.645

4.56

Δ 0.30

8.0

93.163

3.66

Δ 0.05
A Data courtesy of Ref (1). This data developed from algorithms originally published in Ref (2).
Restrictions Imposed by the Conductivity pH Rel </div> </div> </div> </div> <h3>More ASTM standard pdf</h3> <div class=
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