Search results
Results from the WOW.Com Content Network
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:
The absorbance of a material that has only one absorbing species also depends on the pathlength and the concentration of the species, according to the Beer–Lambert law =, where ε is the molar absorption coefficient of that material; c is the molar concentration of those species; ℓ is the path length.
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.
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 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 ...
The attenuation coefficient of a volume, denoted μ, is defined as [6] =, where Φ e is the radiant flux;; z is the path length of the beam.; Note that for an attenuation coefficient which does not vary with z, this equation is solved along a line from =0 to as:
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". [1] Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". [2]
Absorption is a condition in which something takes in another substance. [1] In many processes important in technology, the chemical absorption is used in place of the physical process, e.g., absorption of carbon dioxide by sodium hydroxide – such acid-base processes do not follow the Nernst partition law (see: solubility).