The slurry concentration plays an important role in filtration. Four concepts of concentration are developed

the conventional concentration of slurry 5

which is the mass fraction of solids in slurry from the slurry-tank

the average concentration during filtration Sav defined by Sav =Ws/(ρV + mavWs)

the percentage variation of the average concentratin Eav defined by Eav=| (S-Sav)/S |×100%

and the instantaneous concentration of slurry in filtration St

which is the concentration at cake/slurry interface. On the basis of material balance

the equation of the instan taneous concentration of slurry in filtration is derived as follows: where ρs is the true density of cake solids

ρ the density of filtrate

A the filtration area

V the volume of filtrate

i the number of drainage surfaces

L the thickness of filter-chamber

and εi the porosity at cake/slurry interface which is determined by the Compression-Permeability Cell tes.tThe experiments to measure dV/d(L/i) in the equation were made by use of the experimental apparatus for hydraulic pressure distributions.