Variable time method variation of P with t

Romwalter and Vendl [46] derived a solution to equation (8.67) by differentiating with respect to time and substituting back in the original equation. Brown [47] drew attention to an error in their derivation and. stated that an exact solution for the distribution function appeared to be difficult, if not impossible, to obtain by the above method. 

The following solutions were derived by Robison and Martin [48,49] who used sector-shaped tubes. Their analyses agreed closely with those obtained using the variable height method. 

Miischelknaiitz [5I.52J designed a centrifuge in which the displacement of two diametrically opposed bodies floating in a dispersion was measured. The bodies are fixed on a common rod and are immersed at dilfcrent depths in two chambers. The differential force yields the size distribution directly. Sokalov et. al. [53] described a centrifugal sedimentometer with a float measurement system. 

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