Absorptivity calculation

In gas absorption, the new phase consists of an inert nonvolatile solvent (absorption) or an inert nonsoluble gas (stripping), and normally no reflux is involved. The following paragraphs discuss some of the considerations peculiar to gas-absorption calculations for plate towers and some of the approximate design methods that can be employed when simplifying assumptions are vahd. 

When two or more gases are absorbed in systems involving chemical reac tions, the situation is much more complex. This topic is discussed later in the subsection Absorption with Chemical Reac tion. Graphical Design Method for Dilute Systems The following notation for multicomponent absorption calculations has been adapted from Sherwood, Pigford, and Wilke (Mass Transfer, McGraw-Hill, New York 1975, p. 415) ... 

The absorption problems for other detectors may be considered under three headings (1) attenuation along the beam path, (2) attenuation by the detector window, (3) absorption by the detecting medium. The results of absorption calculations (1.9) in Table 2 1 show the importance of these problems and suggest ways of dealing with them. 

Aqueous solution of a drug (0-10 milli molar) shows a percentage transmission of 50 in a 1 cm cell at 250 run. The molar absorptivity, calculated ... 

Human volunteers were exposed for 24 hours to 2-pyrimidinyl ring-labeled [14C] -diazinon applied to either the forearm or abdomen in either an acetone solution or a lanolin wool grease at doses of approximately 15-20 pg/dose for each application method to test the percutaneous absorption of diazinon. Daily complete void urine samples were collected and analyzed for levels of radioactivity for 7 days after dosing. Percutaneous absorption, calculated from the amount of radioactivity present in the urine, was reported as 2.9-3.85% of the administered dose (Wester et al. 1993). 

The usual practice in gas absorption calculations is to use the overall coefficient Ag in cases where the gas is highly soluble and the overall coefficient Al in cases where the solubility of the gas is low. Ag and Al are interconvertible by using Equation 6.13. 

The relative intensities of absorption calculated may be compared with those observed as an additional check of the method. 

Figure 62. Solid lines contribution of the structural-dynamical model to the dimensionless absorption Astr(v) calculated in the R-band by the ACF method, (a) Calculation for H20, the dimensionless collision frequency Y = 0.6, r/L = 0.27,/) = 2.07. (b) Calculation for D20 with Y = 1.3, r/L = 0.4,/j = 3.54. Dotted lines total absorption calculated for the composite HC-SD model. Temperature 22.2°C. The peak ordinates are set equal to 1.

The following molecular constants are used in further calculations density p of a liquid the static (es) and optical (n ) permittivity moment of inertia /, which determine the dimensionless frequency x in both HC and SD models the dipole moment p the molecular mass M and the static permittivity 1 referring to an ensemble of the restricted rotators. The results of calculations are summarized in Table XXIII. In Fig. 62 the dimensionless absorption around frequency 200 cm 1, obtained for the composite model, is depicted by dots in the same units as the absorption Astr described in Section B. Fig. 62a refers to H2O and Fig. 62b to D2O. It is clearly seen in Fig. 62b that the total absorption calculated in terms of the composite model decreases more slowly in the right wing of the R-band than that given by Eq. (460). Indeed, the absorption curve due to dipoles reorienting in the HC well overlaps with the curve generated by the SD model, which is determined by the restricted rotators. 

The calibration graph at 510 nm is a straight line and Beer s law is obeyed from 0.5 to 5 [xg/ml of boron in the final measured solution (corresponding to 10-110 xg of boron in the aqueous phase). The molar absorptivity, calculated from the slope of the statistical working calibration graph at 510 nm, was 29051/mol/cm. The Sandell sensitivity was 0.011 xgcm2 of boron. The precision of the method for ten replicate determinations was 0.6%. The absorbance of the reagent blank solution at 510 nm was 0.010 d= 0.003 for ten replicate determinations. Therefore, the detection limit was 0.04 xg/ml of boron in the final measured solution. 

Both methods of absorption calculation mentioned are based on the fact that after absorption the drug/metabolites reach the central circulation. In case of oral administered drugs targeting the liver and being eliminated biliary instantly, it is obvious that both methods mentioned fail. In such a special case an absorption estimation might be possible via a biliary excretion study. 

One of the environmental sources of nitrite is represented by the irradiation of nitrate itself. The fact that nitrite, too, is a photoactive compound implies that the photochemical reactivity of nitrate and nitrite cannot often be dissociated, although the relative contributions to hydroxyl generation can be derived from the concentration values, photolysis quantum yields and radiation absorption calculations [6,8,12,14]. 

Figure 6. Variability of intestinal zinc absorption calculated from retention measured on days 7, 14, and 21 after oral administration of Zn to fasting normal volunteers. All measurements were in good agreement values measured on day 7 were slightly less than the mean (—0.79%), those on day 14 slightly more than the mean (- -0.81%), and those measured on day 21 essentially equal to the mean. These small and evenly distributed differences indicate that fecal excretion was more than 99% complete by day 7. The similar variability obtained for each measurement period strongly suggests that most differences were related to measurement variability rather than to delayed fecal excretion.

Table 5d.O supplies the forms for the three terms needed to formulate (GSi)jj, with Ar substituted for As. If in addition, allowance is to be made for the gas not being gray, and are evaluated using values of the emissivity and absorptivity calculated using Table 5-8, and the procedure described in the previous subsection is followed with c.Jct, replacing Ec together with the addition of a clear-gas contribution, when SS is at issue. It is tempting to say that a surface As (or Ar) could be made radiatively adiabatic simply by assigning its reflectance p a value of 1, making the terms in the brackets of Eq. (5-173) much easier to evaluate and the result much simpler. This is valid only if the gas is gray. If it is not, A is a net absorber of radiation...

Several approaches have /been used to determine absorption of trace elements in humans. The most frequently used method has been balance studies, in which the amount of a mineral ingested is compared with the amount eliminated in the feces. However, absorption calculated from total mineral eliminated in fecal collections generally differs greatly from true absorption, since some of the mineral eliminated in the feces is of endogenous origin (1). A number of other difficulties with metabolic balance studies, such as variation in intestinal transit time and inadequate analytical precision, limit their usefulness and often result in conflicting results (2). 

All of our absorption calculations, such as those presented above, have been based on the assumption that the first pulse of excretion represented unabsorbed isotope and subsequent excretion was post-absorptive These absorption values agree with metal absorption determined by other means, such as whole-body counting ... 

Indirect analysis. Colorimetric study of nitric 2 >eroxide dissolved in chloroform. Salet s researches (p. Ill) have shown that the fall of density of nitric peroxide produced by rise of temperature is accompanied by a darkening of the gas, and that the colorimetric results agree with the densimetric if we assume that N2O2 is colourless and NO coloured. Cundall carried out a similar colorimetric study of nitric peroxide dissolved in chloroform, and by its power of absorption calculated how much of the peroxide was in the dissociated form, i. e. as NOg-Ostwald showed that the results are in agreement with the relation... 

Two-photon absorptivities calculated from CNDO/S Cl wave functions for substituted benzenes Power dependence of the MPI and fragmentation of bromobenzene. Mass-resolved studies in qualitative agreement with kinetic model... 

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