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METHOD 9045D 159 " SOIL AND WASTE pH PA +o 1.0 SCOPE AND APPLICATION 1.1 This m thod is an electrometric procedure for measuring pH in soils and waste samples. Wastes ay be solids, sludges, or non-aqueous liquids. If water is present, it must constitute less than 0% of the total volume of the sample. 2.0 SUMMARY F METHOD 2.1 The sainple is mixed with reagent water, and the pH of the resulting aqueous solution is measurec. 3.0 INTERFERECES 3.1 Sampl with very low or very high pH may give incorrect readings on the meter. For samples with a t ue pH of>10, the measured pH may be incorrectly low. This error can be minimized by using low-sodium-error electrode. Strong acid solutions, with a true pH of<1, may give incorrectly igh pH measurements. 3.2 Tempe ture fluctuations will cause measurement errors. 3.3 Errors ill occur when the electrodes become coated. If an electrode becomes coated with an oily aterial that will not rinse free, the electrode can (1) be cleaned with an ultrasonic bath, or (2 be washed with detergent, rinsed several times with water, placed in 1:10 HCI so that the lower third of the electrode is submerged, and then thoroughly rinsed with water, or (3) be cleaned per the manufacturer's instructions. 4.0 APPARATUS ND MATERIALS 4.1 pH met r with means for temperature compensation. 4.2 Glass el ctrode. 4.3 Referen a electrode -- A silver-silver chloride or other reference electrode of constant potential mz y be used. NOTE: Combin tion electrodes incorporating both measuring and referenced functions are conveni nt to use and are available with solid, gel-type filling materials that require minimal aintenance. 4.4 Beaker-r 50-mL. 4.5 Thermometer and/or temperature sensor for automatic compensation. 4.6 Analytic (I balance -- capable of weighing 0.1 g. 9045D - 1 Revision 4 November 2004