# Look Up Table for specific resistance and concentration

Look Up Table for specific resistance and cake concentration of common materials and how they are influenced by the filtration pressure (D Pc).

The equation for average specific resistance (alpha) is:

and, likewise, for cake concentration by volume fraction:

where a o ,C0, n and u are empirically derived constants.
Published values for constants used in above equations
 Material Resistance at 1 bar (m kg-1) a o (m kg-1 Pa-n) n Co (Pa-u) u 100 m m glass beads* 0.064 x109 0.064 x109 0 0.60 0 10 m m glass beads* 6.4 x109 6.4 x109 0 0.60 0 Alumina 5.2x109 2.37x108 0.3 0.07 0.066 Calcium carbonate in salt solution 18.2 x109 46.9 x108 0.13 0.22 0.03 Fine calcium carbonate in water 71 x109 89.3 x108 0.2 0.09 0.1 …end of vacuum filtration range Coarse grade kaolin 71 x109 4.5 x108 0.5 0.15 0.08 Talc in salt solution 112 x109 7.1 x108 0.5 0.008 0.29 Talc in water 112 x109 7.1 x108 0.5 0.088 0.144 Titanium dioxide 344 x109 127 x108 0.32 0.06 0.13 1 m m glass beads* 640 x109 640 x109 0 0.60 0 Cement 491 x109 222 x108 0.3 0.33 0.05 Kaolin (Hong Kong pink) 1025 x109 64.8 x108 0.5 0.17 0.08 zinc sulphide pH 3 1300 x109 1000 x108 0.25 0.19 0.06 …end of pressure filtration range Magnesium hydroxide 1600 x109 135 x108 0.47 Aluminium hydroxide 11000 x109 3320 x108 0.34 Stable zinc sulphide 47000 x109 148 x108 0.92 0.002 0.39 Colloidal clay 63000 x109 1440 x108 0.61
* assuming a random close packing and using the Kozeny-Carman equation

If you would like to calculate a value for specific resistance at your filtration pressure then enter values in the following boxes, using the table values or practical data, and press the calculate button:

 a o    (m kg-1 Pa-n) n pressure drop over the filter cake (Pa)

SELECT       OR YOU CAN       THE ABOVE VALUES

postscript
If you want to know how the average mass of dry cake per unit volume filtrate is obtained from the average cake concentration and the mass fraction of solids in the feed slurry then the following formula is useful. Hence, the filter cake forming pressure influences the volumetric cake concentration and the dry cake mass in a way given by the equations on this page.