It is said that the solubility of a metastable form is difficult or impossible to determine by the usual equilibrium method. In these cases, the solubilities of the metastable form, C_s'*, (calculated) have been estimated by equation (1).
C_s'*=C_s(dC'/dt)/(dC/dt) (1)
where C_s, dC/dt are the solubility and the initial dissolution rate of the stable form., and “^/” is that of the metastable form.
Nogami et al modified the Noyes-Nernst equation to eq. (2), when the dissolution rate is measured by the rotating disk method
dC/dt=(S/V)k_appC_s=(S/V){k_rk_T/(k_r+k_T)}C_s (2)
where S is the surface area of disk, V is the volume of solvent, k_app is the apparent dissolution rate constant and k_r is the rate constant of the interfacial chemical reaction.
The relationship between C_s'* and C_s' is represented by equation (3)
C_s'*=C_s'k_app'/k_app (3)
when k_T is negligible for k_r and k_r', C_s'* is equal to C_s'.
When k_T is not negligible for k_r and k_r', the C_s'* is not equal to C_s'. The cases in which indomethacin, barbital and phenybutazone, C_s'* is not equal to C_s' is discussed.

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Three dimensional particle size classification based on the deposition angle and height in a gas centrifuge which produces a forced vortex was investigated. Different particle trajectories formed a continuous gradation of particle size on the rotor wall. Particles of the size range for which industrial screening is applicable were classified with good resolution. The computed solutions agreed well with the experimental results.

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Based on the particle separation model which has an imaginary cone surface as described definitely in the 1st report, an equation of particle cut size, d_c, for the cyclone of a tangential entry type is derived as follows:
d_c=0.241√μA₀/πρ_pu₀H_cos(θ_c/2)[1.34(D₂/D₁)(1+0.23D₃/D₂)]ⁿRe_u^0.25
Comparisons between the experimental values of 50% separation size, d₅₀, obtained by Smith et al with a five-stage cyclone system for test aerosols and the calculated values of cut size, d_c, by the equation mentioned above, were made; the following expression was obtained as a correction factor for particle agglomeration and re-entrainment from the dust bin:
K_c=d₅₀/d_c=6.3/√Stk
where Stk is a modifid Stokes number and is expressed as,
Stk=w_smv_DH/gd_maxD₃

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