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Description
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Colourless, prismatic crystals or a white or creamy white powder.
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Identification
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-
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Identification 'A'
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A 5% solution in carbon dioxide free water gives reaction of sodium salts
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Identification 'B'
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The solution is colourless and gives reaction of sulphates
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pH
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3.5 to 5.0
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Arsenic
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NMT 4 ppm
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Heavy metals
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NMT 20 ppm
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Iron
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NMT 40 ppm
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Thiosulphate
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Not more than a faint opalescence should produced
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Assay
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NLT 95.0% and NMT 100.5% of Na2S2O5
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