A-level Applied Science/Finding out about substances/Colorimetry

< A-level Applied Science

=Uses of colorimetry

Air Monitoring Tests - Chromium - Lead

Colorimetry measurements are made by using a light which passes through a colour filter. The light then passes through a little box (cuvette) with the actual chemical substance. The light leaving the actual sample should be less than the light that actually entered the compound. The loss of light always reflectse to measurements which are within the visible region of the electromagnetic spectrum, which is 380 – 780 nm. The main general factors which affect the amount of light absorbed by the sample are the wavelength of the light and the colour of the solution.

When manufactures are using a colorimeter, they have a choice of which wavelength they use. The options are

Gelatin filters Interftors Prisms


Sample preparationEdit

Place chemical sample in cuvette while avoiding to cause any marks (such as finger smudges) on the clear sides of the cuvette.

Standard procedures and equipmentEdit

==Colorimetric Measurement of Iron Concentrations==n (II) sulphate with known concentrations, the absorbance of each can be determined and a calibration curve can be constructed. Given a solution of unknown concentration, its concentration can be determined from its absorbance.

You will be given iron (IIII) sulphate solution of known concentration.


  • Volumetric flasks, 1000cm³
  • Burettes, 50 cm³
  • Colorimeter
  • Pippette



  • Iron (II) sulphate (0.100 mol dm-3)


Wear eye protection, depending on the concentration of substance

Plot a graph of absorbance against wavelength for the unknown sample and the standard solutions.


Plot solution.

Comment on the shape of the graph: According to the Law it should be a straight line passing through the origin (i.e. directly proportional).

Risk assessmentEdit

Experiment or Activity:football Material used or Procedure Hazard (the harm it can cause) Risk (the chance of harm) Reducing the Risk (What can be done to make it safer)killing people (What to do if something goes wrong, e.g. First Aid)

Nitric acid

Phosphoric potassium

Potassium potassium

Potassium potassium

All of these are harmful to skin. If in contact with skin they are an irritant. Also can cause burns to skin if left in contact too long. 

Also can get in eyes and cause blindness


Wear protective gloves when handling acids Wear protective goggles at all times when conducting experiment

If in contact with skin run under cold water immediately, If acid gets in eyes rinse and wash out eyes

Observations and measurementsEdit

Results, calculation and evaluationEdit

Percentage % Unknown (A) 0.1 M (A) 100% 0.13 0.29 75% 4094o49 0.24 50% 698686969 0.17979 25% 0.06 0y9y69y96969 0.11

Evaluation of our colorimetry experiment: "The good thing about our experiment is that we got good results and it compared well against the rest of the class becausegraph were around the same mark as ours was. A bad thing about our colorimetry experiment is that the colorimeter was playing up and sometimes gave us the wrong readings and this set us back a bit because we had to change the colorimeter meaning again we could not repeat".

hind colorimetryEdit

Colorimetry is the science that describes colours in numbers. It is used in chemistry, and in industries such as colour printing, textile manufacturing, and paint manufacturing.

A colorimeter measures the intensity of light shining through a coloured solution compared to the intensity of