29. Solving a chemistry problem

25. A blood serum sample is analyzed for potassium content by flame emission spectroscopy using a standard additive. To two aliquots of 5.00 ml was added 5.00 ml of water. An additional 10.0 µl of 0.05 M KCl solution was added to one portion. The emission signals in arbitrary units are 32.1 and 58.6, respectively. What is the serum potassium concentration? Answer: 1.21 * 10-3 mmol / ml.