Ppm is a value that represents the part of a whole number in units of 1/1000000. It is dimensionless quantity, a ratio of 2 quantities of the same unit. The easiest way to do these is to remember the conversion that
1 ppm = 1 mg/L 0.0972 g/100 g H2O = 0.0972/100 mL = 0.972 g/L = 972 mg/L = 972 ppm
