CN110186987B - Universal solution PH value 25 degree conversion method - Google Patents
Universal solution PH value 25 degree conversion method Download PDFInfo
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- CN110186987B CN110186987B CN201910583148.5A CN201910583148A CN110186987B CN 110186987 B CN110186987 B CN 110186987B CN 201910583148 A CN201910583148 A CN 201910583148A CN 110186987 B CN110186987 B CN 110186987B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
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- G01N27/4166—Systems measuring a particular property of an electrolyte
- G01N27/4167—Systems measuring a particular property of an electrolyte pH
Abstract
The invention discloses a universal solution PH value 25 degree conversion method, which comprises the following steps: s1: collecting the pH electrode potential to obtain the pH value of the solution (PHt); s2: collecting a solution temperature value (t); s3: calculating the temperature coefficient (alpha) of the solution PH value, wherein alpha is a (PHt) 2+ b (PHt) + c, a (-0.02 to +0.02), b (-0.5 to 0.5), c (0-1); s4: using the formula: calculating the pH value converted to 25 ℃ by PH 25-PHt/(1 + alpha (t-25)), wherein PH25 is the pH value after temperature compensation, PHt is the pH value measured at temperature t degree, alpha is the temperature coefficient of the pH value of the solution, and t is the temperature of the solution during measurement; s5: the pH at the measurement temperature, the pH at the reference temperature and the measurement temperature are shown. The method has good practicability, and can greatly improve the accuracy of PH measurement at ambient temperature.
Description
Technical Field
The invention relates to the technical field of electrochemical instruments, in particular to a universal temperature compensation method for the pH value of a solution.
Background
The pH value of a solution is an important parameter in the monitoring of life, production process and environment of people, the pH value of various water and solutions is often required to be measured, a measuring cell is usually formed by a glass electrode and a reference electrode for measuring the pH value, and a potential difference Et between the two electrodes is measured by a pH meter
Et＝E0+Kt*pHt
pHt＝(Et-E0)/Kt
In the formula: et is the electrode potential measured at temperature t degree
E0 is the electrode potential at a solution pH of 7
Kt is the slope (conversion factor) of the electrode at the measurement temperature
pHt is the negative logarithm of the activity of hydrogen ions in solution
In the above formula, Et is the electrode potential at the measurement temperature, and the PH obtained by the instrument based on Et is the PH (PHt) at the measurement temperature, however, the PH of the solution varies with the temperature, and if the PH of the solution measured at different temperatures is to be compared or controlled, the PH PHt must be converted to the PH (PH25) at a certain temperature (e.g., 25 ℃) which is generally accepted, otherwise, a large error is caused.
As is well known, the temperature compensation of a conductivity meter in a laboratory can convert the conductivity at the measured temperature into the conductivity value at the reference temperature of 25 ℃, and the function ensures that the conductivity measured by the same solution at different temperatures is comparable, thereby greatly facilitating the data processing in the laboratory.
K25＝Kt/(1+α(t-25))
In the formula: kt is the conductivity value measured at temperature t degree
Alpha is the temperature coefficient of the solution conductivity
t is the temperature of the solution at the time of measurement
K25 is the conductivity value after temperature compensation
But the PH of the solution is much more complex with respect to temperature. When the temperature rises, the pH value of some solutions slightly rises, the pH value of some solutions firstly falls and then rises, the pH value of some solutions is basically unchanged, and the pH value of some solutions obviously falls, namely, the temperature coefficient (alpha) of the pH value of the solution is an unknown number from a positive number to a negative number, so that the temperature compensation function of all pH meters at home and abroad only compensates the influence of the change of the 'conversion coefficient (K)' of a pH electrode on the measurement of a meter, and does not compensate the influence of the temperature on the pH value of a water sample, so that the pH meter can only display the pH value (t) at the actually measured temperature. The measured PH values of the same solution at different temperatures cannot be compared and must be recorded simultaneously with the measured temperature during operation. The data processing, comparison, recording, reporting and industrial control are difficult, and the 25 ℃ conversion of the pH value is to convert the pH value at the current temperature to the pH value at the 25 ℃ temperature which is assumed to be unchanged under other conditions. As long as the solution does not chemically react or the solute volatilizes during the temperature change. This function is currently considered to be impossible, and it is currently widely considered that: because the components of various solutions are different and the temperature coefficients are different, it is impossible for the analyzer to convert the pH value of any solution to 25 ℃.
All laboratory pH meters have the automatic temperature compensation function, but the meters only compensate the influence of temperature on the slope in the measurement of the meters, and do not compensate the influence of temperature on the pH value of a water sample, which causes the pH value of the water sample to be greatly deviated.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides a general method for compensating the pH value of a solution by temperature.
The invention provides a general method for converting the pH value of a solution to 25 ℃, which comprises the following steps:
s1: collecting the pH electrode potential to obtain the pH value of the solution (PHt);
s2: collecting a solution temperature value (t);
s3: calculating the temperature coefficient (alpha) of the solution PH value, wherein alpha is a (PHt) 2+ b (PHt) + c;
s4: using the formula: PH 25-PHt/(1 + α (t-25)) calculated as PH converted to 25 ℃;
s5: the pH at the measurement temperature, the pH at the reference temperature and the measurement temperature are shown.
Preferably, in S3, a (-0.02 to +0.02), b (-0.5 to 0.5), c (0 to 1).
Preferably, in S4, PH25 is the PH after temperature compensation, PHt is the PH measured at temperature t, α is the temperature coefficient of the PH of the solution, and t is the temperature of the solution at the time of measurement.
The invention has the beneficial effects that: the pH value under the solution reference temperature can be developed into a reference pH meter for simultaneously displaying the pH value under the solution measurement temperature and the reference temperature, and the system has important effects on industrial pH control, environmental protection, medical treatment, energy, scientific research and the like.
The common temperature compensation function is to convert the slope obtained by the electrode at the calibration temperature into the slope at the current temperature according to the Nernst formula so as to obtain the pH value (PHt) at the current temperature, and the common temperature compensation function is to convert the pH value at the current temperature into the pH value (PH25) at the temperature of 25 ℃ on the assumption that other conditions are unchanged, so that the pH values measured by the same solution at different temperatures are comparable, and the pH value control in laboratory data processing, comparison, recording and reporting and industrial production and water treatment processes is greatly facilitated.
In industrial production and scientific research work, the requirement on the accuracy of the pH value of a solution is high, the requirement on the measurement accuracy generally reaches 0.01-0.001 PH, when the measurement temperature deviates from the reference temperature (25 ℃), if the measurement accuracy is high, the solution is generally required to be heated or cooled to 25 ℃, which is generally difficult to achieve, the solution is more difficult to achieve in industrial control and environmental monitoring, and the accuracy of the pH measurement at the ambient temperature can be greatly improved by using the reference temperature PH meter.
The method has good practicability, and can greatly improve the accuracy of PH measurement at ambient temperature.
Drawings
FIG. 1 is a schematic diagram of a general pH meter for a 25 degree solution pH conversion method according to the present invention;
FIG. 2 is a diagram showing the pH of 0-50 ℃ pure water HCL HAC NH4CL NaCL NaAC NH3.H2O NaOH in a general method for converting the pH of a solution to 25 ℃;
FIG. 3 shows the compensation effect of 0-50 degree pure water HCL HAC NH4CL NaCL NaAC NH3.H2O NaOH in a general method of converting the pH value of a solution to 25 degrees;
FIG. 4 shows the pH temperature curve (inclined downward) and compensation effect of seawater in a general solution pH25 degree conversion method proposed by the present invention.
Detailed Description
The present invention will be further illustrated with reference to the following specific examples.
Examples
Referring to fig. 1, this embodiment proposes a general method for converting PH of a solution to 25 degrees, which includes the following steps:
s1: collecting the pH electrode potential to obtain the pH value of the solution (PHt);
s2: collecting a solution temperature value (t);
s3: calculating the temperature coefficient (alpha) of the solution PH value, wherein alpha is a (PHt) 2+ b (PHt) + c;
s4: using the formula: PH 25-PHt/(1 + α (t-25)) calculated as PH converted to 25 ℃;
s5: the pH at the measurement temperature, the pH at the reference temperature and the measurement temperature are shown.
In this example, in S3, a (-0.02 to +0.02), b (-0.5 to 0.5), and c (0 to 1), in S4, pH25 is the pH after temperature compensation, PHt is the pH measured at temperature t, α is the temperature coefficient of the pH of the solution, and t is the temperature of the solution during measurement.
We will now take as an example the PH standard buffer solution and other solutions we use in common:
the table shows the pH of the standard buffer solution at 0-50 ℃ and the pH of the instrument after compensation (25 ℃ C. conversion) at the reference temperature (25 ℃ C.), which the reference pH meter will display simultaneously.
If a standard buffer solution with a pH of 12.36 at 25 ℃ is measured at an ambient temperature of 10 ℃, the instrument shows:
TABLE-pH of the Standard buffer solution at 0-50 deg.C
Temperature compensated (25 ℃ C. conversion) pH of standard buffer solution
Table II shows the pH of some aqueous solutions at 0-50 ℃ and the pH at the reference temperature (25 ℃) which the instrument displays after compensation (25 ℃ conversion). The reference PH meter will display both values simultaneously.
The instrument showed, as measured at ambient temperature 40 ℃ in a sodium chloride solution at PH 7.03 at 25 ℃:
pH of the aqueous solution of TABLE II at 0-50 deg.C
Temperature compensated (25 ℃ C. conversion) pH of standard buffer solution
Referring to fig. 2-4, experiments have shown that a "reference PH meter" is a PH meter that can convert the PH of various aqueous solutions to a PH of 25 degrees, and that displays the measured PH (t) at the measured temperature, and also displays the PH (t) at the reference temperature, i.e., a PH (25) at 25 degrees c, and that "reference PH meter" ends the history of "solution PH" being uncompensable.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (2)
1. A general method for converting the pH value of a solution to 25 degrees is characterized by comprising the following steps:
s1: collecting the pH electrode potential to obtain the pH value of the solution (PHt);
s2: the temperature value of the collected solution is 0-50 ℃ (t);
s3: calculating the temperature coefficient (alpha) of the solution PH value, wherein alpha is a (PHt) 2+ b (PHt) + c;
s4: using the formula: PH 25-PHt/(1 + α (t-25)) calculated as PH converted to 25 ℃;
s5: displaying the pH value at the measuring temperature, the pH value at the reference temperature and the measuring temperature;
in the step S4, PH25 is a PH value after temperature compensation, PHt is a PH value measured at temperature t, α is a temperature coefficient of the PH value of the solution, and t is a temperature of the solution during measurement.
2. The universal solution pH25 degree conversion method as claimed in claim 1, wherein in S3, a (-0.02- +0.02), b (-0.5), c (0-1).
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| CN110865105B (en) * | 2019-12-17 | 2020-12-22 | 中国科学院南京土壤研究所 | Method for obtaining soil pH value in-situ calibration curve and application |
| CN113109404A (en) * | 2021-03-15 | 2021-07-13 | 杭州融凯盛科技有限公司 | Method for detecting pH value of glue solution |
| CN113702445A (en) * | 2021-09-03 | 2021-11-26 | 杭州谱育科技发展有限公司 | PH value detection method and water quality analysis method |
| CN114894987A (en) * | 2022-04-07 | 2022-08-12 | 华能上海燃机发电有限责任公司 | Pure water medium pH temperature compensation test method and device |
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Effective date of registration: 20230221 Address after: Floors 1-2, building 4, No. 1628, Lizheng Road, Lingang xinpian District, China (Shanghai) pilot Free Trade Zone, Pudong New Area, Shanghai, 200003 Patentee after: Shanghai Sanxin peirui Instrument Technology Co.,Ltd. Address before: 201715 room 2007, zone J, second floor, building 1, No. 15, Lane 588, zhangliantang Road, Liantang Town, Qingpu District, Shanghai Patentee before: SHANGHAI SAN-XIN INSTRUMENTATION Inc. |