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D664_18 (17a) 04-2018

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Weigh two grams of KHP-- potassium hydrogen phthalate solution-- into a 125-millimeter or suitable-size beaker, and record the weight to the nearest 0.0001 gram, if using weight-based standard. Or pipette 2 milliliters of KHP-- potassium hydrogen phthalate solution-- into a vessel, and add approximately 50 milliliters of carbon dioxide-free water. Titrate the solution to determine the titre of 0.01 moles potassium hydroxide. This volume of KHP-- potassium hydrogen phthalate solution-- will use approximately 2 milliliters of the 0.01 moles potassium hydroxide. Prepare two additional KHP-- potassium hydrogen phthalate solutions-- to standardize the titrant, as in 18.1 of the written standard. Use the three determinations to calculate the average concentration-- moles per liter-- of the potassium hydroxide. The average of the titrant moles per liter determinations should agree, plus or minus 0.0005 moles. Determination of the solvent blank. Adjust the apparatus in accordance with the manufacturer's instructions to provide a dynamic mode of titration. Addition of titrant volume increments should not be greater than 0.2 milliliter. Measure precisely 50 milliliters of isopropyl alcohol using a graduated cylinder, pipette, or automated dispensing device capable of dispensing 50 milliliters plus or minus 0.5 millimeters into a 125-milliliter or suitable-size beaker. Stir the solution and titrate. Record the volume, milliliters of potassium chloride, to plus or minus 0.01 milliliter. Use to titrate to the inflection point. Adjust the apparatus in accordance with the manufacturer's instructions to provide a dynamic mode of titrant addition. Weigh five grams of bio-diesel into a 125-milliliter or suitable-size beaker on an analytical balance, and record the weight to the nearest 0.0001 grams. Measure 50 milliliters plus or minus 0.50 milliliter of IPA, using a pipette or automated dispensing device, into a suitable beaker. Prepare the electrodes as directed in 8.1 of the written standard. Place the beaker or titration vessel on the titration stand and adjust its position so that the electrodes are about half-immersed. Start the stir, and stir throughout the determination at a rate sufficient to produce vigorous agitation without spattering, and without stirring air into the solution. It is important that the same volume of titration solvent, plus or minus 0.5 milliliter, is used for the blank and samples, or inconsistent results can occur. Select the right burette. Fill with 0.01 moles per liter alcoholic potassium chloride solution and place the burette in position on the titration assembly, ensuring that the tip is immersed about 25 millimeters in titration vessel liquid and titrate. On completion of the titration, rinse the electrodes and burette tip with isopropyl alcohol, followed by water. Immerse the electrodes in water for at least 2 minutes before starting another titration to restore the aqueous gel layer of the glass electrode. Rinse the electrodes with isopropyl alcohol prior to running the next sample. If electrodes are found dirty and contaminated, proceed as in 8.1 of the written standard. Store electrodes according to 8.3.3 of the written standard. Multiple titration inflection points are often found during the analysis associated with organic acids, which form over time due to the oxidation of bio-diesel over prolonged storage periods. The volume of titrant for the last well-defined endpoint should be used to calculate the total acidity.

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Duration: 4 minutes and 45 seconds
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Language: English
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Posted by: abuckmaster on Aug 23, 2018

D664_18 (17a) 04-2018

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