Potassium in potassium chloride

ESTIMATION OF POTASSIUM IN POTASSIUM CHLORIDE /

POTASSIUM SULPHATE

Aim 

         To estimate the potassium content in the potassium chloride /potassium sulphate fertilizer.

Principle

         The potassium in the potassic fertilizer solution is measured in a flame photometer.  The flame photometry is based on the measurement of the intensity of light radiation emitted by atoms on excitation when aspirated into a high-temperature flame.

Procedure

a)  Preparation of fertilizer solution

         Weigh accurately 1 g of KCl / K2SO4 sample, transfer it to a 100 ml volumetric flask, dissolve in distilled water, make-up the volume and mix homogeneously.  Pipette out 1 ml of this solution into a 100 ml volumetric flask and make-up the volume with distilled water and mix homogeneously.

b) Preparation of standard solution

         Weigh accurately1.907 g of KCl after drying the salt at 105oC for 2 hours. Transfer it to a 1000 ml volumetric flask, dissolve in distilled water make-up the volume and mix homogenously. This gives the 1000 ppm K solution.  Pipette out 25 ml of the 1000 ppm solution into 250 ml volumetric flask, dilute with distilled water, make-up the volume and mix homogeneously. This gives the 100 ppm solution.  Prepare standards from 10 to 100 ppm by pipetting out 2.5, 5.0, 7.5, 10, 12.5, 15, 15. 17.5, 20, 22.5 and 25 ml of the 100 ppm solution into 25 ml volumetric flask and making up the volume of 25 ml.

a)      Preparation of standard curve

         Adjust the galvanometer or digital reading in the flame photometer to 0 and 100 by aspirating distilled water and 100 ppm K solution into the flame respectively. Then aspirate the standard solutions from 10 to 100 ppm and record the meter readings.  Draw the standard curve with concentration K ppm on the x-axis and meter reading on the y axis. A curvilinear curve will be formed.

d) Measurement of potassium in the fertilizer solution

         Measure the potassium concentration in the fertilizer solution by aspirating the solution into the flame of the meter and recording the meter reading. If the meter reading crosses 100, the fertilizer solution may be diluted suitably.  Using the meter reading the concentration of K in the fertilizer solution may be read from the standard curve. Then compute the potassium content in the fertilizer sample.

Calculations:

Weight of fertilizer taken

:

1 g

Volume of solution made-up

:

100 ml

Volume of aliquot taken for dilution

:

1 ml

Volume of the aliquot diluted

:

100 ml

Concentration of K in the diluted fertilizer solution

:

X ppm