A number in parentheses indicates the year of last reapproval. The principle use of the testis to supplement soil resistivity measurements and therebyidentify conditions under which the corrosion of metals in soilmay be accentuated see G57—78 No other units of measurement are included in thisstandard. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Referenced Documents2.
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A number in parentheses indicates the year of last reapproval. The principle use of the testis to supplement soil resistivity measurements and therebyidentify conditions under which the corrosion of metals in soilmay be accentuated see G57—78 No other units of measurement are included in thisstandard. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
Referenced Documents2. Significance and Use3. Some metals are moresensitive to the pH of their environment than others, andinformation on the stability of a metal as a function of pH andpotential is available in the literature. Most instruments can alsofunction as a high-impedance voltmeter.
An LCD display ispreferred for its readability in a bright, outdoor environment. A few crystals of solidpotassium chloride should always be present within the cham-ber surrounding the calomel to assure that the solution issaturated under the conditions of use. The design of theelectrode must permit the formation of a fresh liquid junctionbetween the solution of potassium chloride and the buffer ortest soil for each test and allow traces of soil to be readilyremoved by washing.
The performance of the glass electrode is satisfactory if itfurnishes the correct pH value However,the requirements outlined above are equally applicable to theelectrodes used in this combination unit. This probe consists of a glass electrode ora combination electrode in a rubber housing at the end of aplastic tube. One type of probe is illustrated in Fig.
Current edition approved May 1, Published June Originallyapproved in Last previous edition approved in as G51—95 A thermometer ofrugged construction is required for soil use, and a stainlesssteel sheathed thermometer is preferred. Metal sheathed ther-mometers come in different lengths, and a length appropriatefor the depth of interest should be chosen. Reagents and Materials5. Thesesolutions, or tablets to make up these solutions, can bepurchased from chemical supply companies or pH equipmentmanufacturers.
The regions of interest, surface,subsurface, or both, where applicable, must be sampled. Calibration and Standardization7. This procedure is as follows Before use, clean and rinse the glass andcalomel electrodes in distilled water. From practicalexperience standard solutions of pH 4, 7, and 8 are recom-mended. A laboratorythermometer can be used for these measurements.
Now adjust the pH meter to read thisknown pH. Immerse the electrodes in thesecond known standard solution and read the pH value. Judgethe system to be operating satisfactorily if the reading obtainedfor the second standard agrees within If a series of measurements are to bemade, repeat the calibration procedure at intervals of about 30min.
Perform the pH meter calibration as follows Otherwise, begin with a standard solution having a pH of 7. If the surface soil pH is desired, then the soilcan be broken up if compacted so as to accept the electrodes. If a subsurface pH is desired, then a boring or an excavationmust be done so that the electrode can be placed in the soil atthe desired depth. The subsurface probe Fig. After boring through thesoil to the depth of interest, carefully lower the probe into thecavity without further preparation of the soil.
This technique is lessdesirable than the probe method described in this section. However, if this must be done, then make the pHmeasurement as quickly as possible after the soil is taken fromthe field. Place the sample in a clean, airtight, glass containeror plastic bag so that the soil is not in contact with any metal.
Make the pH measurement onthe soil at room temperature and as received. However, if a soil isextremely dry with a resistivity exceeding V-cm, acondition not normally encountered, then the pH measurementcannot and should not be made.
This situation will manifestitself with a random drifting of the pH meter reading. Frozen soil manifests itself byrandom drifting of the pH meter reading and is verified by thesoil temperature measurement.
Soil temperature can be determined byinserting a metal sheathed thermometer into the soil to thedepth of interest. This step is important, since poorsoil contact or electrode movement can affect stability of themeasurement. An electrode sepa-ration of about 30 cm is suggested for surface measurements.
For subsurface readings, the reference electrode may be placedon the surface about 30 cm from the bore hole entry. In general, the values will agree within 0. If therange of values is as large as 0. Iftheproblem persists, check your equipment to verify that it isoperating properly, and check your measurement technique asdescribed in Procedure, Section 8, in this test method. Where asoil is extremely dry, it may not be possible to make a pHmeasurement as stated in 8.
Where the soil is frozen, itmust be thawed as indicated in 8. Repeat Calibration ofpH Meter 7. Finally, if erratic readingspersist, it may be necessary to repeat the measurement at a newlocation in the vicinity of interest. Precision and Bias9. Exceptfor the use of only two materials, Practice E was followedfor the design and analysis of the data. Details of the designand analysis of the data are given in the research report.
The respectivestandard deviation among test results may be obtained bydividing the above limit values by 2. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.
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ASTM G51 PDF
Gardajinn Today, some 12, ASTM standards are used around the world to improve product quality, enhance safety, facilitate market access and trade, and build consumer confidence. This standard is also available to be included in Standards Subscriptions. You can download and open this file to your own computer but DRM prevents opening this file on another computer, including a networked server. Information on pH of soil is used as an aid in evaluating the corrosivity of a soil environment. 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. Remember me for one month.
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