D7318_10

Measure the exact concentration of the lead nitrate titrant by titration of the sulfate standard, 8.2 of the written standard. Transfer 1.00 milliliters of the 0.01 molar aqueous sulfate standard solution, 8.2 of the written standard, into a 150-milliliter beaker. Record this volume as V. Add approximately 100 milliliters of denatured ethanol, 7.4 of the written standard, and 1 milliliter of 0.1 molar perchloric acid, 8.6 of the written standard. Prepare the autotitrator for operation. Immerse the electrodes in the titration solution. Initiate stirring and titrate to the potentiometric endpoint with lead titrant. Titration should require approximately 4.0 milliliters of lead solution to reach the endpoint. Record this volume as T. Titrate a blank denatured ethanol sample in the same manner without addition of sulfate standard. Record this volume as T sub b. Calculate the concentration of the lead nitrate titrant as shown in equation 4 of the written standard. The standardization should be repeated until precision comparable to that shown in section 15 and table 2 of the written standard has been achieved, where M sub Pb equals molarity of lead in the titrant, moles per liter; V equals volume of sulfate standard solution added, milliliters, 10.1.1 of the written standard; S equals molarity of the sulfate solution from 8.2 of the written standard, moles per liter; T equals volume of lead titrant used to titrate the sulfate solution, milliliters; and T sub b equals the volume of lead titrant used for the blank, milliliters, 10.2 of the written standard.