AS 5006.1:2019 pdf free.Silver and silver bearing alloys Part 1: Determination of silver content (0.1 % to 99.9 %)-Titrimetric (potentiometric) method.
6 Apparatus
The apparatus shall be as follows:
(a) Glassware.
Grade A volumetric glassware shall be used throughout. The use of volumetric glassware shall
comply with AS 2162.1 and AS 2162.2.
(b) Potentiometric auto-titrator with, or suitable ion-selective electrode meter.
(c) Burette or in the case of an auto-titrator a motor driven plunger or piston type burette linked to an auto-titrator.
(d) Suitable reference electrode capable of determining the point of maximum inflection.
(e) Silver ion-selective electrode, silver metal electrode or combined electrode and reference electrode.
(f) Analytical balance.
Capable of a resolution of 0.01 mg.
(g) Hotplate.
Capable of a temperature of 100 °C.
7 Sample inspection
The sample shall be inspected for the presence of discernible inhomogeneities, contaminants and, in the case of a sample prepared by the vacuum tube method, piping (hollow centre). If any of these defects are present, the sample shall be rejected. If not supplied in a form suitable for assay, the sample shall be flattened to render it suitable for cutting.
8 Procedure
8.1 Number of determinations
Two determinations shall be carried out on the test sample.
8.2 Reference standard
At least one reference standard shall be included with each batch of samples.
8.3 Standardization of potassium chloride solution The procedure shall be as follows:
(a) Weigh and record to 0.01 mg the mass of four quantities of silver [see Clause 5(a)] in the range 250 mg to 500 mg, and place each in individual beakers.
(b) Add 15 mL to 20 mL nitric acid 50 % v/v [see Clause 5(d)] to each beaker, cover with a watchglass and place on a hotplate until the silver has dissolved and brown fumes of oxides of nitrogen gas have ceased.
(c) Allow the beakers to cool to ambient temperature and dilute to 150 mL ± 5 % with water.
(d) Place the beakers on the titrator and immerse the electrodes.
(e) Commence the titration and record the volume of the titrant at the end-point on completion of the reaction. This is detected automatically by an auto-titrator [see Clause 6(b)] and is usually within the range 200 mV to 250 mV. In the case of a manual determination using an ion-selective electrode meter, a graph of mV versus volume of titrant needs to be plotted in order to determine the inflection point.AS 5006.1 pdf download.