The observation of the odor, cold and hot, of samples of surface water
is important as the odors are usually indicative of organic growths or
sewage contamination or both. The odor of some ground waters is caused
by the earthy constituents of the water-bearing strata. The odor of a
contaminated well water is often contributory evidence of its pollution.
A study of the organisms as directed under Microscopical Examination (p.
90) is a valuable adjunct to physical and chemical examination of water.
Certain odors distinguish or identify certain organisms, as, for
example, the “fishy” odor of _Uroglena_, the “aromatic” or “rose
geranium” odor of _Asterionella_ and the “pig pen” odor of _Anabaena_.
Observe and record the odor, both at room temperature and at just below
the boiling point, as follows: