EXPERIMENT 4

The 'Brown Ring' Test for the Detection of Nitrates.

Apparatus

Test tube with 10 cm3 of water and iron.
Sulphate and Conc4 Sulphuric Acid

Method

Place about 10 cm3 of your water sample into a test-tube.

Add a cold saturated solution of iron (ii) Sulphate to the water in the test-tube and mix.

Carefully pour concentrated Sulphuric Acid down the side of the test-tube to form a layer at the bottom.

Result

A brown ring is formed at the junction of the two liquids.

Conclusion

Nitrates are present in the water sample.

The water analysis shows that there are 2.1 mg/litre of nitrates present in the water.