In order to determine the content of calcium and magnesium in an unknown sample of limestone, the utilization of atomic absorption spectrophotometry can help in deciphering the unknown concentrations of each molecule in the limestone sample. Atomic absorption spectrophotometry, emits radiation of the correct frequency that is passed through a flame and the intensity of the transmitted radiation is measured¹.The calcium concentration or ppm can be measured using the absorbance of the solution and comparing it to a standard curve for calcium². Whereas magnesium, needs to be determined using the standard addition method. The concentrations of each respective molecule can be presented as CaO and MgO percentages of the unknown limestone sample.
Materials and Methods
The compound calcium carbonate (CaCO3, CAS: 471-34-1, 204.89ppm) was utilized to compare its absorbance to the unknown sample of limestone # 8066 on the standard curve. Moreover, magnesium sulfate heptahydrate (MgSO4*7H2O, CAS: 10034-99-8, 40.8ppm) was also utilized to compare its absorbance against that of the unknown. Lab personnel from the CSU Eastbay department of chemistry stockroom performed all calibrations on the Perkin Elmer AAnalyst 300 atomic absorption spectrometer.
All chemicals used in this experiment were obtained from the CSU Eastbay department of chemistry stockroom. A Denver Instrument Co. Sargent-Welch analytical balance was used to determine the mass of the unknown, mass of calcium carbonate, and mass of magnesium sulfate heptahydrate. A Perkin Elmer AAnalyst 300 atomic absorption spectrometer equipped with a Lumina Calcium and Magnesium Lamp was used to determine the absorbance. The instrument used Argon and Acetylene as the carrier gas and oxidant gas, respectively.
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