Improvement of Official Chemical Analysis of Tea (Part 2) : Examination of Water Extract Determination

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The accuracy of analytical method and the personal error of analyst were examined with A.O.A.C. method for determining water extract in tea.<BR>The accuracy of analysis was computed as C. V. 1.63% ; the error accompanied with a single determination by an analyst was C. V. 3.17% and that with a mean value of double determinations by an analyst was C. V. 2.96%.<BR>By modifying some procedures, the following operation is decided as the official method for determining water extract in tea.<BR>Add 200ml. of hot water to 2g. of pulverized tea in a 500ml. flask, and reflux slowly on an electric heater or gas flame for 2 hours.<BR>Cool in current water, make up the volume to 500ml., and filter through dry paper (Toyo No. 2). Transfer 50ml. aliquot into a weighed bottle and evaporate to dryness on a steam bath. Place in an oven (98-100°C) and dry to a constant weight.