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

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14-02-2014

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American Society for Testing and Materials

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CONTAINED IN VOL. 11.01, 2018 Defines the precise on-line determination of pH in water samples of conductivity lower than 100 [mu]S/cm over the pH range of 3 to 11, under field operating conditions.

Committee	D 19
DocumentType	Redline
Pages	11
PublisherName	American Society for Testing and Materials
Status	Current

1.1This 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

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).

FIG. 1 Restrictions Imposed by the Conductivity pH Relationship

1.2This test method includes the procedures and equipment required for the continuous pH measurement of low conductivity water sample streams including the requirements for the control of sample stream pressure, flow rate, and temperature. For off-line pH measurements in low conductivity samples, refer to Test Method D5464.

1.3The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

ASTM E 2635 : 2014 : REDLINE	Standard Practice for Water Conservation in Buildings Through In-Situ Water Reclamation
ASTM D 1193 : 2006 : R2018	Standard Specification for Reagent Water
DIN ISO 13065 E : 2017	SUSTAINABILITY CRITERIA FOR BIOENERGY (ISO 13065:2015)
ASTM D 6569 : 2014 : REDLINE	Standard Test Method for On-Line Measurement of pH (Withdrawn 2023)
ASTM D 5464 : 2016 : REDLINE	Standard Test Method for pH Measurement of Water of Low Conductivity
BS ISO 13065:2015	Sustainability criteria for bioenergy
DIN ISO 13065:2017-06	SUSTAINABILITY CRITERIA FOR BIOENERGY (ISO 13065:2015)
ASTM D 1293 : 2018 : REDLINE	Standard Test Methods for pH of Water
ASTM D 1193 : 2006 : R2011	Standard Specification for Reagent Water
ASTM D 1193 : 2006	Standard Specification for Reagent Water
ISO 13065:2015	Sustainability criteria for bioenergy

ASTM D 1129 : 2013 : REDLINE	Standard Terminology Relating to Water
ASTM D 2777 : 2013 : REDLINE	Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
ASTM D 4453 : 2017 : REDLINE	Standard Practice for Handling of High Purity Water Samples
ASTM D 5464 : 2016 : REDLINE	Standard Test Method for pH Measurement of Water of Low Conductivity

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ASTM D 5128 : 2014 : REDLINE

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

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