1. Colorimetric determination of manganese in steel

2. Colorimetric analysis
type of visible spectroscopy
used to determine the concentrations of coloured solutions
coloured substances absorb light of a colour complementary to their own
a single wavelength of light is used
the amount of light absorbed is proportional to the concentration of the substance

3. Colorimetric determination of manganese in steel
Manganese in steel can be converted into permanganate
ions by oxidising with
nitric acid, Mn(s) Mn2+(aq) + 2e-
potassium periodate,
Mn2+(aq) + 4H2O(l) MnO4-(aq) + 8H+ + 5e-
the colour develops during the second step; the mixture should be heated until the intensity of the pink colour remains constant
permanganate solution appears purple because it absorbs
green light and transmits red and blue thus a green filter
( nm) is used

4. Colorimetric determination of manganese in steel
Optically matched cuvettes are used to ensure that any
absorption by the cuvette is kept constant
A calibration curve is prepared where the absorbance of
known concentrations of permanganate is measured