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11. Place beaker on the hotplate and heat the solution to boiling to drive <br />off any dissolved CO2, then cool the solution to room temperature. <br />12. Titrate the solution with 0.0100 N NaOH, that is free to C02 and <br />protected from the atmosphere, Lo pH 7.0 using a pH meter. <br />3.2.11.6 Calculations- <br />1. meq H{J100 g = (ml of NaOH) X (N of NaOH) X (1009/weight of sample), <br />2. x S = 0.0185 (meq H+/1009) - 0.0806. (Grubs, et al., 1973). <br />3. To convert percent sulfur (x S) to maximum Ca003 equivalents: Multiplj+ <br />x8 by 31.25 to get tone CaC03 equivalent/1000 tone of material. <br />3.2.12 Double Acid &xtrnetable Phosphorus, Potnseium, Calcium, and Mameaium <br />3.2.12.1 Principle-- <br />The method i• a modified North Carolina Double Acid Method first published <br />by Mehlich (1953) end then by Nelson, Mehlich end Winters (1953). <br />Phosphorus, potassium, calcium, sad magnesium are extracted from the sample <br />using s solution containing dilute hydrochloric sad aulitiric acid. <br />Phosphorus concentration is the extract is determined using a colorimeter <br />and Calibration curve. The concentrations op potassium, calcium, and <br />magnesium in the extract are determined using an atomic absorption apectro- <br />photameter sad calibration curve. The concentrations of each element can <br />then be converted into pounds/1000 tons by calculations. <br />3.2.12.2 Camments- <br />With some soils a light to dark yellow color may develop is the extract. <br />Decolorization !e accomplished by the addition of activated charcoal in <br />the extraction procedure. Lenthnnum is added ae a compeneatiag element <br />to remove phosphate sad sulfate interference in the atomic absorption <br />spectrophotometer methods for calcium end magnesium. <br />After the initial extractiaa, individual elements can be determined if <br />data for all four elements are not required. Samples with elements higher <br />is concentration than given in the calibration curves moat be diluted end <br />the resulting reading multiplied by the dilution Yactor. <br />3.2.12.3 Chemicale- <br />1. Hydrochloric acid (HC1), concentrated. <br />2. Sulfuric acid (H2SO4), concentrated. <br />3. Extracting solution: To make 0.05 N HC1 and 0.025 N H2SO4, measure <br />about 10 liters deionized water into an 18 liter pyrex bottle. Add 12 ml <br />A2604 (96x) end 73 ml HC1 (37x). Make to 18 liters with distilled water <br />and mix thoroughly by shaking. Alloy 12 hours to come to equilibrium. <br />72 <br />