Benzene and phenol
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What are the quantities ou use when you carry out a test for a phenol with iron(III) chloride?
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Corrie writes .....
Here's a couple of recipes from well-known books on organic chemistry tests - you'll see they differ quite a bit!
First of all you'll need to neutralise the iron(III) chloride solution (usually made up using HCl to prevent hydrolysis) by adding sodium carbonate or ammonia solution dropwise, until a feint precipitate (of iron(III) hydroxide) just forms.
One recipe says add the the neutral iron(III) chloride solution to a about 1 g or 1 cm3 of the test substance until no further colour change occurs - a blue-violet colour is seen with most phenols.
The other method, which I would favour, says add 1 drop of the iron(III) chloride solution to a very dilute aqueous solution or minute crystal of the phenol, to produce the same blue-violet colour.
Take your pick, or try both!
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updated: 17 November 2008
