ANALYTICAL cHEMISTRY - Iv

MSCM302

Determination of mixture of alkali metals by flame photometry.

The principle of flame photometer is based on the measurement of the emitted light intensity when a metal is introduced into the flame. The wavelength of the colour gives information about the element and the colour of the flame gives information about the amount of the element present in the sample.
Flame photometry is one of the branches of atomic absorption spectroscopy. It is also known as flame emission spectroscopy. Currently, it has become a necessary tool in the field of analytical chemistry. Flame photometer can be used to determine the concentration of certain metal ions like sodium, potassium, lithium, calcium and cesium etc. In flame photometer spectra the metal ions are used in the form of atoms.
The compounds of the alkali and alkaline earth metals (Group II) dissociate into atoms when introduced into the flame. Some of these atoms further get excited to even higher levels. But these atoms are not stable at higher levels.
Hence, these atoms emit radiations when returning back to the ground state. These radiations generally lie in the visible region of the spectrum. Each of the alkali and alkaline earth metals has a specific wavelength.

Borosil beakers (100 ml) 20 Nos., Standard measuring flasks (100 ml) 2 Nos., Flame photometer, etc.

NaCl, KCl, Conductivity water, etc.

Standard solutions:

(Sodium): Dissolve 2.542 g sodium chloride in 1 litre deionized water in a graduated flask. 1 ml ≡ 1.0000 mg (Given).
(Potassium): Dissolve 1.906 g of potassium chloride in 1 litre deionized water in a graduated flask. 1 ml ≡ 1.0000 mg (Given).

Working standards:

(Sodium): Place 4 ml of 1000 ppm standard solution of sodium into 100 ml measuring flask and dilute it 100 ml by conductivity water. Concentration of this solution will be 40 ppm.
(Potassium): Place 4 ml of 1000 ppm standard solution of sodium into 100 ml measuring flask and dilute it 100 ml by conductivity water. Concentration of this solution will be 40 ppm.

Prepare 6 sets of solutions containing varying quantities of sodium and potassium ions as given in the table.
Adjust the oxidizing flame of flame photometer. Select sodium filter and adjust zero reading with conductivity water and set 100 emittance with 40 ppm working standard solution. Measure the emittance of each of the solution.
Select potassium filter and adjust zero reading with conductivity water and set 100 emittance with 40 ppm working standard solution. Measure the emittance of each of the solution.
Plot emittance against concentration. These are the standard curves of sodium and potassium ions. Determine concentration of sodium and potassium ions present in the mixture solution by recording the emittance of the individual ions present in the mixture solution using the appropriate filters. Calculate the amount of individual ions from the standard curves.

To determine the Na & K ion using Flame Photometer_1.mp4

To determine the Na & K ion using Flame Photometer_2.mp4

G H Jeffery, J Bassett, J Mendham and R C Denney, Vogel's Textbook of Quantitative Chemical Analysis, 5th Edition
S. Suzanne Nielsen, Food analysis, 4th Edition

Dr. Viraj Bhanvadia,

Assistant Professor, Chemistry,

viraj.bhanvadia@gsfcuniversity.ac.in

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