14. The test should be carried out without adjustment of pH. If there is evidence of marked
change in the pH of the tank water after addition of the test substance, it is advisable that the test be
repeated, adjusting the pH of the stock solution to that of the tank water before addition of the test
substance. This pH adjustment should be made in such a way that the stock solution concentration
is not changed to any significant extent and that no chemical reaction or precipitation of the test
substance is caused. HC1 and Na0H are preferred.