Practical limits of some standard chemical analyses in pollution control

On the basis of selected examples it is shown that chemical analyses performed according to the Polish Norms can produce incorrect results. The sources of errors were disclosed and some improvements suggested. The pH-measurements of acid rains and water samples with conductivity less than 25 μS/cm, the COD (dichromate) determination especially of saline wastes, the BOD determination by the dilution method, the BOD and COD as the indexes of organic matter content, and the TOC determination as a helpful index for troublesome samples were discussed.