Solids suspension factors affecting

All the drugs in any solid dosage form or suspension when administered will first change into drug solution in body fluids. So, dissolution rate is important factor affecting the rate of absorption. 

To obtain the absolute sound attenuation in the coal slurry, the diffraction loss, the acoustic mismatch loss, the attenuation due to the Teflon window, and the oil coupling must be calculated. Thus, it is difficult to accurately determine the absolute attenuation. In practice, one measures the relative attenuation with respect to a standard. The attenuation of ultrasonic waves in a solid suspension is attributed to three major factors, namely, scattering, viscosity, and thermal effects. Although the presence of particles affects the fluid viscosity and thermal conductivity, the primary source of attenuation may be due to particle scattering. Hence, one may define the relative attenuation of the HYGAS coal slurry by comparing the slurry attenuation with that of the carrier fluid, i.e., the toluene/benzene mixture. This can be expressed by the equation... 

The viscosity of slurries is a function of the solution and solid involved, as well as the slurry density. The viscosity can also be significantly affected by the particle size, size distribution, and particle shape. As a general rule, as particle shape varies from spheres to needles, the viscosity moves further from Newtonian behavior. A detailed discussion of factors affecting the viscosity of suspensions can be found in Sherman (1970). 

Factors Affecting the Absorption of Drugs from Solid Dosage Forms and Suspensions... 

Several theoretical and empirical relationships have been proposed to describe the viscosity of suspensions in Newtonian or non-Newtonian viscous liquids. These relationships have also been used, with ranging degrees of success, to correlate viscosity data when the suspending medium is viscoelastic [62]. In the following various relationships are reviewed. The viscosity of Newtonian as well as non-Newtonian suspensions is affected by the characteristics of the solid phase such as shape, concentration and dimensions of the particles, its size distribution, flie nature of the surface, etc. The influence of each of these factors is examined below. 

A number of empirical equations have been obtained for the rate of sedimentation of suspensions, as a result of tests carried out in vertical tubes. For a given solid and liquid, the main factors which affect the process are the height of the suspension, the diameter of the containing vessel, and the volumetric concentration. An attempt at co-ordinating the results obtained under a variety of conditions has been made by Wallis 8 . ... 

Hirsekorn and Miller (H2) made visual qualitative observations of the suspension of solids by paddle agitation in very viscous liquids (to about 50,000 cp.). For low impeller Reynolds numbers (about 10) in geometrically similar systems (6-, 12-, 18-in. vessels) the major factor in effecting particle suspension appeared to be power input per unit volume. In any given case the power required for complete suspension of all the particles was affected by system geometry and the settling velocity of the solids. No detailed correlation of the observations was presented. 

The macroscopic properties of liquid suspensions of fumed powders of silica, alumina etc. are not only affected by the size and structure of primary particles and aggregates, which are determined by the particle synthesis, but as well by the size and structure of agglomerates or mesoscopic clusters, which are determined by the particle-particle interactions, hence by a variety of product- and process-specific factors like the suspending medium, solutes, the solid concentration, or the employed mechanical stress. However, it is still unclear how these secondary and tertiary particle structures can be adequately characterized, and we are a long way from calculating product properties from them [1,2]. 

Soil pH measurement is usually affected by a number of factors viz. salt concentration, soil-water ratios, suspension effect etc. The use of O.Ol(M) CaClg solution yields stable readings in pH-measurements. The hydrogen ions in the soil system are distributed between solid and liquid phases as follows. The dynamic equilibrium may be represented as follows. 

The interfacial properties of colloidal suspensions are determined by the chemical reactions (e.g. protonation) and adsorption of solutes. Additionally, the interface can be affected by the dissolution-precipitation equilibrium of the particle phase. This is because precipitation changes the surface morphology (Vigil et al. 1994) or leads to phase transition (Lefevre et al. 2002 Carrier et al. 2007). In addition, dissolution means degradation of the particles and may result in the loss of the finest particle fractions (i.e. Ostwald ripening). For this reason, it is necessary to understand the factors governing the dissolution of solid particles. 

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