Practical investigations
Read our general notes on Risk Assessment
I want to determine % of iron in iron tablets using colorimetric method for my project, and compare it with normal titration. I am not sure how to make solutions and work out ppm.
Ulex says ...
Your first problem is that iron(II) has a very pale colour in solution and there are no strongly-coloured and soluble complexes suitable for colorimetry
Probably the best starting point would be to convert the iron(II) to iron(III) and then to add sodium thiocyanate which forms an intense red complex with iron(III) ions. You may have to dilute the solution to stop it being virtually opaque. Note that you will have to do all the mixing and dilutions accurately and quantitatively.
Make up a series of solutions of iron(II) of different concentrations, convert these to iron(III) and add sodium thiocyanate to each. Try them in the colorimeter, choosing a suitable filter, to get a calibration curve of readings against concentration. Standardise your procedure at every stage. Then you can use the calibration curve to find the concentration of your unknown solution.
Before you start any practical work, carry out a risk assessment and check with your teacher.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
back to Practical investigations
Rate this page or react
Share your views on this page, 9 ratings so far
, rated at 
updated: 10 December 2003
