Preparation of plant sample solution by dry combustion

Method 7.11a. Preparation of plant sample solution by dry combustion 

Method 7.11b. Determination of potassium in piant materiai by fiame photometry (dry ashing extract) 

Calculation. Subtract the blank reading from the sample reading in pg K ml read from the graph. This is equal to the g kg of potassium in the sample. Divide the pg K mM by 10 to obtain the % K in the sample. If the sample was not oven-dried, use the separate moisture determination to correct the result to K in DM. 

Explanation 2 g sample was dissolved in 50 ml solution (x 25 v/m dilution), which was further diluted by a factor of 40 (2.5 ml to 100 ml). Thus the 2-g sample would have been diluted to 50 ml x 40 = 2 I, which is 1 g sample M. Therefore, 1 kg sample would be present in 10 I sample solution. If the measured concentration is y pg K ml this is equivalent to 10 y pg K b or 10 = y pg K in 10 I, which is y g K in 10 I sample solution, which we have shown to contain 1 kg sample. 

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