Detail of GB/T 8151.26-2023

Introduction of GB/T 8151.26-2023

GB/T 8151.26-2023 Methods for chemical analysis of zinc concentrates-Part 26: Determination of silver content-Acid dissolution and flame atomic absorption spectrometric method 1 Scope This document specifies an acid dissolution and flame atomic absorption spectrometric method for the determination of silver content of zinc sulfide concentrates. The document is applicable to the determination of silver in zinc sulfide concentrates containing up to 60% (m/m) zinc in the form of zinc blende and related materials. The method is applicable to silver contents from 10 g/t to 500 g/t. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 385 Laboratory glassware - Burettes Note: GB/T 12805-2011 Laboratory glassware - Burettes (ISO 385 :2005, NEQ) ISO 648 Laboratory glassware - Single-volume pipettes ISO 1042 Laboratory glassware - One-mark volumetric flasks Note: GB/T 12806-2011 Laboratory glassware - One-mark volumetric flasks (ISO 1042:1998, NEQ) ISO 3696 Water for analytical laboratory use - Specification and test methods. Note: GB/T 6682-2008 Water for analytical laboratory use - Specification and test methods (ISO 3696 :1987, MOD) ISO 4787 Laboratory glassware – Volumetric instruments - Methods for testing of capacity and for use ISO 9599, Copper, lead, zinc and nickel sulfide concentrates - Determination of hygroscopic moisture content of the analysis sample - Gravimetric method Note: GB/T 12810-2021 Laboratory glassware - Capacity methods testing and use of volumetric instruments (ISO 4787 : 2010, NEQ) ISO 9599 Copper, lead, zinc and nickel sulfide concentrates - Determination of hygroscopic moisture content of the analysis sample - Gravimetric method Note: GB/T 27674-2011 Copper, lead and zinc sulfide concentrates - Determination of hygroscopic moisture in the analysis sample - Gravimetric method (ISO 9599 :1991, IDT) 3 Terms and definitions There are no terms and definitions defined in this document. 4 Principle Decomposition of the concentrate in hydrochloric and nitric acids. Dissolution of the digestion residue in hydrochloric acid and measurement by flame atomic absorption at 328.1 nm. 5 Reagents During the analysis, use only reagents of recognized analytical grade and water that complies with grade 2 of ISO 3696. 5.1 Silver metal, wAg ≥ 99.99%. 5.2 Nitric acid, p20=1.42 g/ml, chloride content<0.5 mg/ml. 5.3 Nitric acid (1+1) To 250 ml of water carefully add, with stirring, 250 ml of nitric acid (5.2). 5.4 Hydrofluoric acid, p20=1.16 g/ml to 1.19 g/ml. 5.5 Hydrochloric acid (1+4) To 800 ml of water carefully add, with stirring, 200 ml of hydrochloric acid (5.4). 5.6 Ammonia solution, (p20=0.89 g/ml). 5.7 Ammonia solution (1+3) To 750 ml of water add, with stirring, 250 ml of ammonia solution (5.6). 5.8 Silver standard solutions 5.8.1 Silver standard solution (1000μg/ml). Weigh 0.5000g of silver metal (5.1) into a 250 ml conical beaker, add 50 ml of nitric acid (5.3), cover, and heat gently until the metal dissolves. Remove the cover and evaporate gently to near dryness. Add 250 ml of hydrochloric acid (5.4) and warm until the solution clears. Cool, and transfer to a 500 ml volumetric flask. Dilute to volume with water and mix thoroughly. This solution should be freshly prepared, unless it is being used on a regular basis. 5.8.2 Silver standard solution (100 μg/ml) Pipette 10 ml of silver standard solution (5.8.1) into a 100 ml volumetric flask containing 45 ml of hydrochloric acid (5.4). Dilute to volume with water and mix thoroughly. Standard solutions should be prepared at the same ambient temperature as that at which the determinations will be conducted. Silver standard solutions should be stored in brown glass bottles. 5.9 Calibration solutions To six 100 ml volumetric flasks, each containing 20ml of hydrochloric acid (5.4), add from a burette(6.2) 0 ml, 1 ml, 2 ml, 3 ml, 4 ml, and 5 ml of silver standard solution (5.8.2). Dilute to volume with water and mix thoroughly. These standards contain 0 μg, 1μg, 2μg, 3μg, 4μg, and 5μg of silver per ml and shall be freshly prepared. Calibration solutions should be prepared at the same ambient temperature as that at which the determinations will be conducted. 6 Apparatus Ordinary laboratory apparatus and the following. a) Volumetric glassware, of class A complying with ISO 385, ISO 648, and ISO 1042 and used in accordance with ISO 4787. b) Burette, grade A 10 ml capacity, capable of being read to 0.02 ml. c) Atomic absorption spectrometer (AAS), equipped with a glass bead in the spray chamber rather than a flow spoiler d) Balance, precision analytical, capable of being read to 0.1 mg. 7 Samples 7.1 Test sample Prepare an air-equilibrated test sample in accordance with ISO 9599. Note: A test sample is not required if predried test portions are to be used (see Annex A). 7.2 Test portion Taking multiple increments, extract a test portion from the test sample in such a manner that it is representative of the whole contents of the dish or tray. Weigh to the nearest 0.1 mg approximately 1g of test sample. At the same time as the test portion is weighed, weigh test portions for the determination of hygroscopic moisture in accordance with ISO 9599. Alternatively, the method specified in Annex A can be used to prepare predried test portions directly from the laboratory sample. 8 Procedure 8.1 Number of determinations Carry out the determinations at least in duplicate and as far as possible under repeatability conditions on each test sample. Note: Repeatability conditions exist where mutually independent test results are obtained with the same method on identical test material in the same laboratory by the same operator using the same equipment within short intervals of time. 8.2 Blank test Carry out a blank test in parallel with the analysis using all reagents specified in the determination but omitting the test portion. The purpose of the blank test in this method is to check the quality of the reagents. If a significant blank value is obtained as a result of the blank test, check all reagents and rectify the problem. 8.3 Decomposition of test portion Transfer the test portion to a 250 ml conical beaker and moisten with 1 ml of water. All glassware should be washed in ammonia (5.7) and rinsed with water prior to use to remove any silver adhering to the glass surface. Add 35 ml of nitric acid (5.3), cover with a watch glass, and heat at a low temperature until the reaction ceases. Note: Temperature-controlled electric heating plate should be used for low-temperature heating, and the control temperature should be about 150 ℃. Add 10 ml of hydrochloric acid (5.4), raise the cover slightly, and evaporate to dryness. Remove from the hotplate and cool. Add a further 10 ml of hydrochloric acid (5.4) and again evaporate to dryness. Rapid heating can cause samples to splatter or spit. Care should be taken to ensure that this does not occur. Re-dissolve in 25 ml of hydrochloric acid (5.5). Heat to boiling, remove from the hotplate and cool. Transfer the solution to the volumetric flask indicated in Table 1 by washing and diluting to volume with hydrochloric acid (5.5).

Contents of GB/T 8151.26-2023