Standard methods for the examination of water and sewage

by American Public Health Association. Laboratory Section; American Chemical Society; Association of Official Agricultural Chemists

REPRESENTATIVE SAMPLES.

Care should be taken to obtain a sample that is truly representative of the liquid to be analyzed. With sewages this is especially important because marked variations in composition occur from hour to hour. Satisfactory samples of some liquids can be obtained only by mixing together several portions collected at different times or at different places—the details as to collection and mixing depending upon local conditions.