How to prepare your own pH buffers for pH meter calibration from scratch

This video shows you how to prepare pH 4 and pH 7 buffers for pH meter calibration using readily available low cost raw salts. These buffers have a strength of 0.1M. These are the amounts needed to prepare 250mL of buffer solution:
pH 4
Potassium Citrate 2.63g
Citric acid monohydrate 3.45g
(if using anhydrous citric acid, use 3.15g)
pH 7
Potassium Citrate 7.14g
Citric acid monohydrate 0.35g
(if using anhydrous citric acid, use 0.32g)
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Class A Volumetric Flask (250mL)
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Beaker set
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Scale
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Citric Acid Monohydrate
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Citric Acid (anhydrous)
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Potassium Citrate
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Silicon ice cube trays (similar, but not exact ones shown in video)
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