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The concentration of sites is given by dividing the total number of sites (S 0) covering the whole surface by the area of the adsorbent (a): [ S 0 ] = S 0 / a . {\displaystyle [S_{0}]=S_{0}/a.} We can then calculate the concentration of all sites by summing the concentration of free sites [ S ] and occupied sites:
Variable pathlength absorption spectroscopy uses a determined slope to calculate concentration. As stated above this is a product of the molar absorptivity and the concentration. Since the actual absorbance value is taken at many data points at equal intervals, background subtraction is generally unnecessary.
The absorption coefficient is fundamentally the product of a quantity of absorbers per unit volume, [cm −3], times an efficiency of absorption (area/absorber, [cm 2]). Several sources [ 2 ] [ 12 ] [ 3 ] replace nσ λ with k λ r , where k λ is the absorption coefficient per unit density and r is the density of the gas.
The same relationship is also applicable for the concentration of a solute adsorbed onto the surface of a solid and the concentration of the solute in the liquid phase. In 1909, Herbert Freundlich gave an expression representing the isothermal variation of adsorption of a quantity of gas adsorbed by unit mass of solid adsorbent with gas ...
The ratio of the absorbance at 260 and 280 nm (A 260/280) is used to assess the purity of nucleic acids. For pure DNA, A 260/280 is widely considered ~1.8 but has been argued to translate - due to numeric errors in the original Warburg paper - into a mix of 60% protein and 40% DNA. [6] The ratio for pure RNA A 260/280 is ~2.0. These ratios are ...
where U is the internal energy, p is the pressure, V is the volume, T is the temperature, S is the entropy, and μ i is the chemical potential of the i-th component. By taking the total derivative of the Euler form of the Gibbs equation for the α phase, β phase and the surface phase:
The amount concentration c is then given by = (). For a more complicated example, consider a mixture in solution containing two species at amount concentrations c 1 and c 2 . The decadic attenuation coefficient at any wavelength λ is, given by μ 10 ( λ ) = ε 1 ( λ ) c 1 + ε 2 ( λ ) c 2 . {\displaystyle \mu _{10}(\lambda )=\varepsilon _{1 ...
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...