ISO 15248 pdf download.Zinc sulfide concentrates — Determination of silver and gold contents — Fire assay and flame atomic absorption spectrometric method using scorification or cupellation
1 Scope
This International Standard specifies a fire assay and flame atomic absorption spectrometric procedure for the determination of silver and gold contents of zinc sulfide concentrates. The method is applicable to the determination of silver and gold 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 1 0 g/t to 500 g/t and gold contents from 0,1 g/t to 1 2 g/t.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 385-1 :1 984, Laboratory glassware — Burettes — Part 1 : General requirements . ISO 648:1 977, Laboratory glassware — One-mark pipettes . ISO 1 042:1 998, Laboratory glassware — One-mark volumetric flasks . ISO 3696:1 987, Water for analytical laboratory use — Specification and test methods . ISO 4787:1 984, Laboratory glassware — Volumetric glassware — Methods for use and testing of capacity . ISO 9599:1 991 , Copper, lead and zinc sulfide concentrates — Determination of hygroscopic moisture in the analysis sample — Gravimetric method .
3 Principle
Fire assay fusion of a test portion to produce a lead button, which is scorified to reduce it to a mass of 2 g to 5 g. Retreatment fusion of the primary fusion and scorification slags to produce a low-silver content lead button which is scorified to approximately 2 g to 5 g. Dissolution of both lead buttons in nitric acid and filtration of the solution. Dissolution of the filter paper plus gold and determination of silver and gold by flame atomic absorption spectrometry.3.2 Cupellation Fire assay fusion of a test portion to produce a lead button, which is cupelled to produce a bead of silver and gold. Retreatment fusion of the primary fusion slag and spent cupel to produce a second bead of silver and gold. Dissolution of both beads in dilute nitric acid and filtration of the solution. Dissolution of the filter paper plus gold and determination of silver and gold by flame atomic absorption spectrometry.
4 Reagents
During the analysis, use only reagents of a recognized analytical grade and water that complies with grade 2 of ISO 3696. Wash all glassware with aqua regia followed by water and 25 % ammonia. A chloride-free environment is recommended. 4.1 Sodium carbonate, anhydrous 4.2 Litharge, assay reagent grade having silver content less than 0,2 g/t, and gold content less than 0,01 g/t 4.3 Silica, precipitated grade 4.4 Potassium nitrate or sodium nitrate 4.5 Flour 4.6 Nitric acid ( ρ 20 1 ,42 g/ml), chloride content < 0,5 µg/ml 4.7 Nitric acid wash solution, (5 ml/l) To 995 ml of water add 5 ml of nitric acid (4.6). 4.8 Nitric acid, (250 ml/l) To 1 500 ml of water carefully add, with stirring, 500 ml of nitric acid (4.6) and cool. 4.9 Hydrochloric acid, ( ρ 20 1 ,1 6 g/ml to 1 ,1 9 g/ml). 4.10 Borax, fused anhydrous sodium tetraborate 4.11 Silver metal, minimum 99,99 % purity 4.12 Gold metal, minimum 99,99 % purity 4.13 Aqua regia Mix 3 parts of hydrochloric acid (4.9) with 1 part of nitric acid (4.6); prepare freshly as required. 4.14 Ammonia solution Add 500 ml of ammonia solution ( ρ 20 0,89 g/ml) to 500 ml of water. 4.15 Standard solutions NOTE Standard solutions should be prepared at the same ambient temperature as that at which the determinations will be conducted.4.15.1 Silver standard solutions 4.15.1.1 Silver standard solution, (1 000 µg/ml) Weigh 0,500 0 g of silver metal (4.1 1 ) into a 400 ml beaker, add 1 00 ml of nitric acid (4.8), cover and heat gently until the metal dissolves. Continue heating to remove oxides of nitrogen. Cool, and transfer to a 500 ml volumetric flask. Dilute to volume with water and mix thoroughly. This solution should be stored in a brown bottle.