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If the conductivity meter does not have automatic temperature correction, the sampling <br /> technician can use the following formula to correct the conductivity reading for temperature: <br /> K - Em <br /> 1 + 0.0191(t - 25) <br /> Where: <br /> • K=corrected conductivity in µmhos/cm <br /> • Em = measured conductivity in µmhos/cm <br /> • t =temperature in °C <br /> The conductivity of a solution is a function of the concentration and charge of the ions in <br /> solution and of the rate at which the ions move under the influence of an electrical potential. <br /> As the ionic strength increases, the rate at which the individual ions move decreases. <br /> Conductivity varies linearly with ionic strength for values below 1,000 µmhos/cm. As <br /> conductivity increases above 5,000 µmhos/cm, the line curves significantly; beyond 50,000 <br /> µmhos/cm,the conductivity is an unsatisfactory index of ionic concentration. <br /> B.9.5. Apparatus <br /> • Conductivity meter <br /> • Conductivity check solutions (Normally, a 10,000 µmhos/cm solution will cover the range of <br /> expected sample conductivity) <br /> B.9.5.1. Calibration <br /> • Calibrate the conductivity probe according to manufacturer's specifications. <br /> • Rinse the temperature probe and conductivity cell with distilled or deionized water. <br /> • Place the temperature probe and conductivity cell in TDS standard and allow the readings to <br /> stabilize. Record the temperature and conductivity reading in the field data sheet book. <br /> • If the reading is within ±10 percent of the accepted value, the cell/instrument calibration <br /> check is acceptable. <br /> • If the cell/instrument calibration check is unacceptable, consult the instrument operation <br /> manual for cell cleaning and instrument trouble-shooting procedures. <br /> B.9.5.1.1. Procedure <br /> These calibration procedures are as listed in the instrument handbook. <br /> • When filling the calibration vessel prior to performing the calibration procedure, make <br /> certain that the level of the calibration standard is high enough in the calibration cup to <br /> cover the entire conductivity window. <br /> • After placing the probe in the calibration solution, agitate it to remove any air bubbles. <br /> • Allow the reading to stabilize. <br /> • Calibrate the meter to 10,000 µmhos/cm. <br /> Daub &Associates, Inc. Page B-24 Natural Soda LLC 2022 SAP <br />