Procedure of Test
This procedure uses a wavelength of 420 nm and a cell with a light path of approximately 10-mm. First prepare a calibration curve for the photometer using successive dilutions of the sulfate standard to adequately cover the range of sulfate in the samples to be tested. The dilutions of the standard should be treated in exactly the same manner as that shown below for analysis of the water samples. Using a 50-ml plastic graduate, add 50 ml of sample to a 125-ml glass flask. …..