Inorganic reactions
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How can I test for nitrates in water?
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Ulex writes
I presume you are working in the area of possible pollution of water from the use of nitrate fertilisers. The problem is that concentrations are likely to be very low which makes test results difficult to obtain.
There are two common tests for nitrates which you should look up in textbooks of inorganic chemistry or, possibly, using Google:
1. Reduction with Devarda’s Alloy or aluminium powder. The test solution is boiled with powdered alloy or aluminium powder and sodium hydroxide solution. Ammonia is evolved, which can be tested for or collected and titrated (for a quantitiative determination).
2. The 'Brown Ring' test. This must be carried out under supervision as it involves concentrated sulphuric acid used in rather an unusual way. Unless done carefully, nasty accidents are possible. Please get your teacher to advise.
Personally, I don’t think either of these will suit your purpose. It is possible to buy indicator test strips which will detect low concentrations of nitrate ions. It is also possible to buy an instrument called a comparator which will do the job electronically. A firm called ‘Kittiwake’ offers advice. Try an internet search.
Risk assessment
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updated: 21 February 2008
