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In physics and engineering, permeation (also called imbuing) is the penetration of a permeate (a fluid such as a liquid, gas, or vapor) through a solid.It is directly related to the concentration gradient of the permeate, a material's intrinsic permeability, and the materials' mass diffusivity. [1]
Example of a dissolved solid (left) Formation of crystals in a 4.2 M ammonium sulfate solution. The solution was initially prepared at 20 °C and then stored for 2 days at 4 °C. In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent.
Class III – low permeability, high solubility . Example: cimetidine; The absorption is limited by the permeation rate but the drug is solvated very fast. If the formulation does not change the permeability or gastro-intestinal duration time, then class I criteria can be applied. Class IV – low permeability, low solubility . Example: bifonazole
The drug apparent permeability (P app) is calculated by normalizing the drug flux (j) over the initial concentration of the API in the donor compartment (c 0) as: Equation 2: = / Dimensionally, the P app represents a velocity, and it is normally expressed in cm/sec. The highest is the permeability, the highest is expected to be the ...
Here, the green substance has a greater solubility in the lower layer than in the upper layer. The partition coefficient , abbreviated P , is defined as a particular ratio of the concentrations of a solute between the two solvents (a biphase of liquid phases), specifically for un- ionized solutes, and the logarithm of the ratio is thus log P .
A practical unit for permeability is the darcy (d), or more commonly the millidarcy (md) (1 d ≈ 10 −12 m 2). The name honors the French Engineer Henry Darcy who first described the flow of water through sand filters for potable water supply. Permeability values for most materials commonly range typically from a fraction to several thousand ...
Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. How the membrane is constructed to be selective in its permeability will determine the rate and the permeability. Many natural and synthetic materials which are rather thick are also semipermeable.
Solubility equilibrium – Thermodynamic equilibrium between a solid and a solution of the same compound; Total dissolved solids – Measurement in environmental chemistry is a common term in a range of disciplines, and can have different meanings depending on the analytical method used. In water quality, it refers to the amount of residue ...