State any five tests that is conducted on a water sample to check its purity?

Question

and state the one that is most reliable

Answer 1

If you are talking about purity in drinking terms then, being limited to 5 tests,  you must use broad screening tests. So:

1. Bacteriological analysis (to determine the absence of e.g. Coliform bacteria)

2. Electrical conductivity - indicates (though does not identify)the level of dissolved salts, Cl-, NO3-, SO4=, Na+,Ca++ etc..

3. pH - Should be between say 6.0 to 8.5, though nearest to 7.0 is best.

4. Dissolved oxygen - normal levels of dissolved O2 ( about 9.5 - 10 mg/l) cannot exist if the water is significantly contaminated with many substances.

5. Specific gravity - if water is pure, it MUST have an SG of 1.0. The introduction of any dissolved substance in any quantity will have to give an SG of greater than 1.

Hope this helps.

Answer 2

I don't know.