PERCENTAGE CONCENTRATION: Concentrations in excess of 10000mg/L are generally expressed in terms of percent, for conveniences. For practical purposes, the conversion of 1 percent = 10000 mg/L be used even though the density of the solutions are slightly more than that of pure water (10000mg/L = 10000mg/1000000mg = 1 mg/100 mg = 1 percent).
The concentration of salts in seawater is about 35000mg/L. To convert to percent salts, divide by 10,000 obtaining 3.5 percent. The concentration of wastewater sludge may be about 3 percent solids. To convert this to mg/L, multiply by 10,000 getting 30000mg/L solids.
A concentration expressed in terms of percent may be also computed using the following expression. Percent = (Mass of Solute (mg)/ Mass of Solvent (mg)) X 100