DETERMINATION OF CHLORIDE IN THE HALOGENS DISTILLATE ANALYSIS BY AMPEROMETRIC MICROTITRIMETRY
Scope
This test method covers the determination of halogens, except fluorine, as separated by steam distillation of uranyl nitrate solutions. The detection limit is 1.5 µg Cl/g U.
Summary of Test Method
An aliquot of the distillate equivalent to about 2.0 g of uranium and adjusted to pH 8 is concentrated and titrated by constant current coulometric generation of silver ions to an amperometric end point. Standards are run to determine the calibration factor in µg Cl - /s, and the total halides … in the sample, excluding fluorides, are determined .. reported as chloride.
Equipments
Automatic Chloride Titrator- This procedure is based upon the use of the Cotlove chloride titrator.
Reagents
· Nitric Acid (0.5 N)-Acetic Acid (1+4) solution. Place 500 mL of water, 35 mL of HNO3, and 200 mL of CH3COOH in a 1 L flask and dilute to volume.
· Prepare a dry gelatin mixture of 60+1+1 gelatin,thymol blue, and thymol. Store in test tubes in a refrigerator until used. Add 6.2 g of dry mixture to 1 L of hot water, and heat with stirring until solution is clear.
· Chloride, Standard Solution (1 mL = 10 µg Cl). Dilute 10 mL of chloride stock solution to 1 L with the HNO3-CH3COOH solution.
· Chloride, Stock Solution (1 mL = 1 mg Cl). Dissolve 0.2103 g of potassium chloride (KCl) in water and dilute to 100 mL.
Procedure
· Prepare the titrator for use in accordance with the instruction manual and check it for proper operation.
· Pipet 20 mL of the blank distillate into a 30 mL beaker.
· Evaporate to 5 mL on a hot plate.
· Add 5 mL of the HNO3-CH3COOH solution and 0.5 mL of gelatin solution.
· Place the beaker in position on the titrator and follow the instructions with the instrument to conduct the titration in the low position.
· Record the time.
· Repeat step 2 through step 6 until blank values are constant.
· Pipet another 20 mL aliquot of the blank distillate into a 30 mL beaker and add 2 mL (20 µg) of the chloride standard solution. Repeat step 3 through step 6 to obtain the calibration factor.
· Pipet a 20 mL aliquot of the sample distillate into a 30 mL beaker and repeat as in step 3 through step 6’
Calculation
· Calculate the calibration factor, F, in micrograms of chloride per second as follows
F = (20 µg Cl -) / (A-B)
Where
A = time of titration of standard, s
B = time for titration of blank, s
· Calculate the halogen content in micrograms of chloride per gram of uranium as follows
Chloride, = F (C-B) / D
Where
B = time for titration of blank, s
C = time for titration of sample, s
D = uranium contained in the titrated sample, g
F = calibration factor.
Precision
At the low levels encountered with this material the precision is ± 20% of the amount present.
Literature
ASTM-C799, Standard Methods for “Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical analysis of Nuclear-Grade Uranyl Nitrate solution”
Scope
This test method covers the determination of halogens, except fluorine, as separated by steam distillation of uranyl nitrate solutions. The detection limit is 1.5 µg Cl/g U.
Summary of Test Method
An aliquot of the distillate equivalent to about 2.0 g of uranium and adjusted to pH 8 is concentrated and titrated by constant current coulometric generation of silver ions to an amperometric end point. Standards are run to determine the calibration factor in µg Cl - /s, and the total halides … in the sample, excluding fluorides, are determined .. reported as chloride.
Equipments
Automatic Chloride Titrator- This procedure is based upon the use of the Cotlove chloride titrator.
Reagents
· Nitric Acid (0.5 N)-Acetic Acid (1+4) solution. Place 500 mL of water, 35 mL of HNO3, and 200 mL of CH3COOH in a 1 L flask and dilute to volume.
· Prepare a dry gelatin mixture of 60+1+1 gelatin,thymol blue, and thymol. Store in test tubes in a refrigerator until used. Add 6.2 g of dry mixture to 1 L of hot water, and heat with stirring until solution is clear.
· Chloride, Standard Solution (1 mL = 10 µg Cl). Dilute 10 mL of chloride stock solution to 1 L with the HNO3-CH3COOH solution.
· Chloride, Stock Solution (1 mL = 1 mg Cl). Dissolve 0.2103 g of potassium chloride (KCl) in water and dilute to 100 mL.
Procedure
· Prepare the titrator for use in accordance with the instruction manual and check it for proper operation.
· Pipet 20 mL of the blank distillate into a 30 mL beaker.
· Evaporate to 5 mL on a hot plate.
· Add 5 mL of the HNO3-CH3COOH solution and 0.5 mL of gelatin solution.
· Place the beaker in position on the titrator and follow the instructions with the instrument to conduct the titration in the low position.
· Record the time.
· Repeat step 2 through step 6 until blank values are constant.
· Pipet another 20 mL aliquot of the blank distillate into a 30 mL beaker and add 2 mL (20 µg) of the chloride standard solution. Repeat step 3 through step 6 to obtain the calibration factor.
· Pipet a 20 mL aliquot of the sample distillate into a 30 mL beaker and repeat as in step 3 through step 6’
Calculation
· Calculate the calibration factor, F, in micrograms of chloride per second as follows
F = (20 µg Cl -) / (A-B)
Where
A = time of titration of standard, s
B = time for titration of blank, s
· Calculate the halogen content in micrograms of chloride per gram of uranium as follows
Chloride, = F (C-B) / D
Where
B = time for titration of blank, s
C = time for titration of sample, s
D = uranium contained in the titrated sample, g
F = calibration factor.
Precision
At the low levels encountered with this material the precision is ± 20% of the amount present.
Literature
ASTM-C799, Standard Methods for “Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical analysis of Nuclear-Grade Uranyl Nitrate solution”
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