Solubility versus particle size

The solubilities of A9-tetrahydrocannabinol were determined (7) by two methods 1) Beer s law plots were obtained by plotting the absorbance at one wavelength (225 nm) versus the amount of tetrahydrocannabinol added. The solubility of tetrahydrocannabinol was determined as that concentration at which deviation from Beer s law was observed 2) A modification of the procedure of Saad and Higuchi (11) for determining solubility by using a particle-size counter was also used ... 

Discuss the conditions of formation, particle size, crystallinity, moisture content, [Fe(III)/OHJ solid ratio, and thermodynamic stability of Fe(lll) oxyhydroxide solids such as ferrihydrite and goethite. What happens to the solution pH, stoichiometry, and solubility of such solids when they are precipitated and aged under acid versus under alkaline conditions ... 

Silicosis-Pncumoconiosis-Fibrinogencsis Mechanism of silicosis, Amorphous versus crystalline silica and particle size. Susceptibility to silicosis. An unusual compound in silico tic tissues, Solubility theory. Silica antagonists to prevent silicosis Asbestosis-Microaciculosis BeneFicial Effects of Silica Silicon Metabolism Silica Gel as a Culture Medium Organosilicon Compounds Analytical Problems Conclusion References... 

Particle Growth. The monomer concentrations after points 1-L can be used to calculate the size of the colloidal particles versus time. In the molybdate test, the unrcactivc fraction corresponds to colloidal silica, and the reactive fraction is monomer or soluble silica. Using the graph of Figure 3.57 relating particle size and solubility (taken from Figure 3.32) the calculated particle size versus time is shown in Figure 3.58. 

One of the main reasons to investigate co-crystals is to increase the solubility of a poorly soluble compound (BCS Class 2 and 4). For neutral molecules, cocrystals can certainly expand the solid forms possible for development, while for a free acid or free base, both salts and co-crystals can be used to improve the solubility profile. There are a number of considerations when discussing solubility data. The first is equilibrium versus kinetic (or apparent) solubility measurements. Kinetic solubility values are approximate values usually based on one measurement at one time point. Unless preliminary experiments have been performed, it is not known if equilibrium has been reached in the time frame used. For equilibrium solubility, a number of time points and measurements are taken to ensure that the solution has reached equilibrium as evidenced by a plateau in the concentration data. This is sometimes called powder dissolution. The time required to reach the equilibrium solubility can also be a factor in development based on the residence time in the stomach and intestines. It is desirable for the drug to dissolve while it is in the gastrointestinal tract and very long dissolution times may result in less absorption of the drug. Powder dissolution rates can also be dependent on particle size therefore the intrinsic dissolution rate may be a better assessment of this parameter. 

As in the case of emulsion polymerization, an increase in the functional monomer concentration leads to a reduction in the final hydrodynamic particle size and enhanced water-soluble polymer formation, as illustrated in Figures 9.15 and 9.16 for the batch polymerization of NIPMAM/MBA/ IDA/KPS. The reduction in particle size versus functional monomer has been attributed to the enhancement of precursor formation and the number of stable particles, which rapidly become the polymerization loci. 

On storage, several breakdown processes may occur that depend on the particle size distribution and the density difference between droplets and the medium. It is the magnitude of the attractive versus repulsive forces that determines flocculation. The solubility of the disperse droplets and the particle size distribution determines Ostwald ripening. The stability of the liquid film between the droplets determines coalescence phase inversion [1]. The various breakdown processes are illustrated in the figure 6.1. 

Figure 4.12 Excipient percolation thresholds (expressed as %v/v HPMC + initial porosity)/ HPMC relative particle size versus the drug solubility in matrices containing acyclovir, theophiline, ranitidine HCl, acetaminophen, lobenzarit disodium and KCl.

Figure 13.5 Size-dependent state diagram reduced temperature (T/Tc) versus solubility Cg in the interval from 0 to 0.5. Points show the usual cupola-shaped diagram of a binary system for the case of separation in an infinite system (when = Cptx)-Points represent the first stable solution of Equation 13.12 and indicate the cupola-shaped diagram of a small particle at a fixed radius R (the line connecting the...

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