Practical investigations
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I need to find the percentage iron, in cast iron, using a dichromate titration. What is the best way to dissolve the iron to form iron(II) without it oxidising to iron(III)?
Ulex says
The way to do this is to use an excess of dilute sulphuric acid. In neutral solution iron(II) ions, first hydrolyse to iron(II) hydroxide which then oxidises to iron(III) hydroxide. The use of excess sulphuric acid suppresses the hydrolysis so that the oxidation is much less likely to occur. The titration requires the presence of acid anyway so adding plenty at the dissolving stage has a double benefit.
Always carry out a risk assessment and check with your teacher before starting any practical work.
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.
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updated: 14 March 2007
