ASTM C760-90(R2020) pdf free download
ASTM C760-90(R2020) pdf free download.Standard Test Methods for Chemical and Spectrochemical Analysis of Nuclear-Grade Silver-Indium-Cadmium Alloys
7. Scope
7.1 This test method is applicable to the determination of silver, indium, and cadmium in alloys of approximately 80 % silver, 15 % indium, and 5 % cadmium used in nuclear reactor control rod applications. The titrimetric methods presented 6,7 will yield results with a bias of the order of 0.1 %. 7.2 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
8. Summary of Test Method
8.1 A weighed sample is dissolved in nitric acid and diluted to a known volume, and aliquots are removed for analysis. Silver is determined first by titrating with standardized sodium chloride solution to the potentiometric endpoint indicated by a chloride-selective ion electrode. Following the silver titration, the solution is boiled to coagulate the silver chloride. The pH is adjusted to 2.5 and the indium content is titrated with EDTA, using PAN (1-(2-pyridylazo)-2-naphthol) indicator. The pH is then raised to 6.0 and the cadmium is titrated with EDTA using the same indicator. The entire process requires approximately 20 min per aliquot, exclusive of sample weighing and disso- lution.
11. Reagents
11.1 Ammonium Hydroxide (sp gr 0.90)—Concentrated am- monium hydroxide (NH 4 OH). 11.2 Buffer Solution, pH4—0.5 M sodium acetate—0.5 M acetic acid. 11.3 Cadmium (Cd)—Metal, >99.99 % pure. 11.4 Ethylenediaminetetraacetate Dihydrate Disodium Salt (EDTA) Solution (0.01000 M)—Weigh 3.722 6 0.001 g of EDTA into a small plastic beaker. Dissolve with water, transfer quantitatively to a 1-Lvolumetric flask, and make up to volume with water. Transfer the solution to a plastic storage bottle. Do not allow the EDTA solution to stand in contact with glass containers. 11.5 Indium (In)—Metal, >99.99 % pure. 11.6 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO 3 ). 11.7 PAN Indicator Solution (0.1 % PAN in Methanol)— Dissolve 100 mg of 1-(2-pyridylazo)-2-naphthol in 100 mL of methyl alcohol and mix until completely dissolved. 11.8 Silver (Ag)—Metal, >99.99 % pure. 11.9 Sodium Chloride (NaCl). 11.10 Sodium Chloride Solution (0.0500 M)—Dry sodium chloride (NaCl) at 120°C, in a weighing bottle, to a constant weight and cool to room temperature in a desiccator. Weigh 2.922 6 0.001 g of the dried NaCl into a small plastic beaker. Dissolve in water, quantitatively transfer to a 1-L volumetric flask, and make up to volume with water.
12. Standardization
12.1 Silver-Indium-Cadmium Calibration Standard: 12.1.1 Clean approximately 8.0 g of silver metal, 1.5 g of indium metal, and 0.5 g of cadmium metal with an organic solvent and air dry. 12.1.2 Weigh each metal accurately and transfer to a 100-mL beaker. 12.1.3 Add sufficient water to cover the metal pieces and add HNO 3 (sp gr 1.42) dropwise until dissolution is complete. 12.1.4 Transfer quantitatively to a 100-mL volumetric flask and dilute to volume with water. 12.2 Calibration ofNaCl and EDTA Titrants: 12.2.1 Pipet 10 mL of the calibration standard into a 100-mL volumetric flask and dilute to volume with water. (Retain this solution as a working standard.) 12.2.2 Pipet 10 mL of the diluted standard into a 100-mL beaker and adjust the volume to about 25 mL with water. 12.2.3 Adjust the pH to approximately 1 using NH 4 OH (sp gr 0.90). 12.2.4 Place a TFE-fluorocarbon-coated stirring bar in the solution and insert the chloride specific ion electrode and the reference electrode.
12.2.5 Stir at a moderate rate and titrate the silver with NaCl solution. Record millivolt readings versus volume added. Allow sufficient time for equilibrium readings to be attained. 12.2.6 The titration end point is taken as the termination of the rapidly rising segment of the millivolt versus volume titration curve. 12.2.7 Adjust to pH 2.5 6 0.2 by dropwise addition of acetate buffer solution (pH4). 12.2.8 Remove the electrodes and rinse thoroughly to avoid loss of indium and cadmium. 12.2.9 Heat the solution to boiling on a hotplate until the supernatant liquid is clear. Allow to cool. 12.2.10 Add 4 drops ofPAN indicator solution. The solution should be deep purple.
