High concentration effects

Several investigations have been carried out on the settling behavior of spherical particles in concentrated suspensions [7] with best agreement with equations of the form (6.84). Equations similar to (6.85) indicate too high a concentration dependency on settling rate. Apparatus for carrying out hindered settling experiments [61] was described in 1960, modified apparatus was described in 1970 [62] and experimental procedure in 1977 [63]. 

There are various ways of dealing with experimental data [47,64] 

Apply equation (6.89) combined with Stokes equation to find an uncorrected particle radius.  

Apply equation (6.92) and plot [ ,( -f)] against s to find w, and equation (6.87) to find 6(e) and a corrected particle radius  

Dollimore and Heal [65] applied method 2 to determine the thickness of the film on the outside of the particles. Ramakrishna and Rao [66] criticize this approach and prefer method 3. In a later discussion [67] they stated that their criticism was because equation (6.92) was being used outside its range of validity (i.e. at 0.8) and in this region equation (6.89) must be used. Pierce [68], in the same discussion, suggested the use of equation (6.87). 

---

Various excipients with parenteral use Hemolytic effects with rat blood (e.g., >1%-hydroxypropyl- 3-CD, >2.5%-PEG 400, >5%-propylene glycol, >0.125%-Tween 80) May be related to high-concentration effect 60... 

The amount of the coupling product was found to be dependent upon the concentration of the dihalide in the metal-ammonia reductions, perhaps because of local high concentration effects. The oxidation of camphene by t-butyl perbenzoate in the presence of Cu salts affords, after saponification of the reaction mixture, nojigiku alcohol (458), among other products. ... 

Arden, T. V. and Rowley, M. Anion-exchange in uranyl sulphate solution. High concentration effects and rate studies. J. Chem. Soc. p. 1709 (1957). 

---