BSF3232-METHOD VALIDATION&VERIFICATION 11415

This method is used to determine the percentage of

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This method is used to determine the percentage of water in a sample  by drying the sample to a constant weight. The water content is  expressed as the percentage, by weight, of the dry sample.  Sampling: Select a representative quantity of the moist wood sample based on the  maximum particle size of the sample.  Procedure:  Determine linearity of the balance (calibration). The external calibration of the  balance used states that the difference from the actual weight on the scale pan  and the reading on the scale is within  ±  0.5 mg (or 0.0005 g) with a  95%  confidence. Under the normal distribution, a  95%  confidence gives a factor of  1.96.  ii. Determine repeatability (precision) during measurements using the balance.  Ten (10) repeated measurements of a tare weight and gross weight gave a  standard deviation of 0.258 mg at a range of 10,000.6 mg to 10,001.4 mg.  iii. Determine the net weight of the wood sample by substracting the tare (empty  boat) weight of the measuring boat from each measurement (in both wet  weight measurements and dry-weight measurements)  12
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CONFIDENTIAL BSK/BSB/BSP/1 4151/BSF3232  iv. Determine the net weight of the moisture by substracting the weight of wet  sample with the weight of dried sample after the heat dry in the hot plate at  115 ° C until a steady / constant dry weight is achieved.  Calculation:  The moisture content of the wood sample is calculated using the following equation:  %W=  A-B  x 100%  Where:%W =Percentage of moisture in the sample  A = Weight of wet sample (miligrams)  B Weight of dry sample (miligrams)  Measurement Results:  Summary of the measurement results (x) and values of combined uncertainties, u(x)  and the relative combined uncertainty u(x) / x, are shown in the table below.  Description Values (x) u(x) u(x) / x  Weight of wood (mg) before 5,854 0.386 0.0001  drying  Weight of wood (mg) after 5,698 0.386 0.0001  drying [10 Marks]  13 
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