Sedimentation is the experimental studying of settling. There are several stages in the settling of flocculated suspension, and different zones are formed as sedimentation proceeds. At first zone, the solid is uniformly distributed in the liquid, after short the solids have settled to give a zone of clear liquid. The settled solid zone is the bottom zone. The zone that the solid is distributed in the liquid is distributed zone and the between of the distributed zone and the bottom zone is transition zone. Plotting graph between clear liquid interface height and settling time, the first region is negative linear line after that it approaches to zero. The slope of the first region is the velocity of settling and the second one is constant. From the Stokes’ law u t = gD2 p(p- )/18µ, at part 1 the more amount of limestone, the more time settling, but the velocity is constant. Increasing amount of limestone has no result with velocity of settling. At part 2, when add the coagulant (KAl(SO4).12H2O) in the slurry, the coagulant affects to the distributed limestone to flocculate easily, that is similar to the density of limestone higher, the higher density of particles in liquid, the higher settling velocity from the Stokes’ law.