Water residue maps

Another feature of a residue map we would like to illustrate is the representation of systems that form two liquid phases. In Fig, 6.3 we show how mixtures of vinyl acetate and water form two liquid phases with drastically different compositions. We can take advantage of this nonideality to help produce pure acetic acid from a single distillation column. In Fig. 6.4 we show how the net feed to a column can be changed by mixing the original feed with the vinyl acetate rich reflux. The new feed composition contains less acetic acid acid and water and more vinyl acetate. When we look at the residue curves that pertain to the new feed composition, we find that they move over areas with little water. Most of the feed water is rejected with the overhead vapors... 

N, is the normalization factor, n, and are parameters depending on the atomic type. Pi are the multipolar population parameters and k and k are the contraction-expansion coefficients [11] for, respectively, spherical and multipolar valence densities. We have chosen orthogonal reference axes which respect the tetrahedral (23) T point group for Si and A1 atoms of the scolecite in order to reduce the number of multipolar parameters only the cubic harmonic multipoles (one octupole / = 3 and two hexadecapoles / = 4) have been refined for these two atoms. The pseudo-atom expansion was extended to the octupoles (/ = 3) for 0 including oxygen of water, and to the dipoles (/ = 1) for H. The best radial functions of Si and A1 atoms were obtained by inspection of the residual maps [12], ( / = 4,4,4,4 (1 = 1-4)) s were taken from Clement and Raimondi [13] i si = 3.05 bohr, = 2.72 bohr. For 0 atoms, = 4.5 bohr and the multipole exponents were respectively n = 2, 3, 4 up to the octupole level. 

Fig. 5. The acetone—2-propanol—water system where I represents the 2-propanol—water azeotrope, (a) Residue curve map (34) (b) material balance lines...

Fig. 11. Separation of nitric acid, HNO, and water, H2O, using sulfuric acid, H2SO4, as the solvent, (a) Residue curve map and material balance lines where...

Fig. 16. Residue curve map calculated for the ethanol—water—benzene mixture where A is the end poiat of the vapor line I represents a homogeneous...

Podebush Sequence forPthanol—Water Separation. When ethyl acetate is used as the entrainer to break the ethanol—water azeotrope the residue curve map is similar to the one shown in Figure 21d, ie, the ternary azeotrope is homogeneous. Otherwise the map is the same as for ethanol—water—benzene. In such... 

More Complex Mixtures. AH the sequences discussed are type I Hquid systems, ie, mixtures in which only one of the binary pairs shows Hquid—Hquid behavior. Many mixtures of commercial interest display Hquid—Hquid behavior in two of the binary pairs (type II systems), eg, secondary butyl alcohol—water—di-secondary butyl ether (SBA—water—DSBE), and water—formic acid—xylene (92). Sequences for these separations can be devised on the basis of residue curve maps. The SBA—water—DSBE separation is practiced by ARGO and is considered in detail in the Hterature (4,5,105,126). 

FIG. 13-58 (Continued) Residue curve maps, (h) MEK-MIPK-water system containing two minumum-hoiling binary azeotropes. 

FIG. 13-73 Residue curve maps for acetone-methanol systems, (a) With water, (h) With MIPK. 

The transformed variables describe the system composition with or without reaction and sum to unity as do Xi and yi. The condition for azeotropy becomes X, = Y,. Barbosa and Doherty have shown that phase and distillation diagrams constructed using the transformed composition coordinates have the same properties as phase and distillation region diagrams for nonreactive systems and similarly can be used to assist in design feasibility and operability studies [Chem Eng Sci, 43, 529, 1523, and 2377 (1988a,b,c)]. A residue curve map in transformed coordinates for the reactive system methanol-acetic acid-methyl acetate-water is shown in Fig. 13-76. Note that the nonreactive azeotrope between water and methyl acetate has disappeared, while the methyl acetate-methanol azeotrope remains intact. Only... 

FIG. 13-76 Residue curve map for the reactive system methanol-acetic acid-methyl acetate-water in chemical eqiiihhriiim. 

Exposures of Children. Data need to be developed to properly assess the exposure of infants who eat processed baby foods containing residues of pesticides such as endosulfan. Several studies have estimated exposure based on endosulfan concentration found in foods typically eaten by infants however, no studies that directly studied infant exposure could be located. Attention should also be given to infant formulas and to the tap water used to prepare infant formulas from condensed or powdered forms. More data are also required to properly assess endosulfan exposure to children who live, play, or attend school near farmlands that are treated with endosulfan. Maps that catalog endosulfan use on crops and present average application rates would better allow an assessment of the potential for children in farming communities to be exposed. The possibility that farming parents work clothes and shoes may carry endosulfan residues into the home also should be studied. In addition, home use of endosulfan, which may result in exposure of children, needs to be investigated. 

With data averaged in point group m, the first refinements were carried out to estimate the atomic coordinates and anisotropic thermal motion parameters IP s. We have started with the atomic coordinates and equivalent isotropic thermal parameters of Joswig et al. [14] determined by neutron diffraction at room temperature. The high order X-ray data (0.9 < s < 1.28A-1) were used in this case in order not to alter these parameters by the valence electron density contributing to low order structure factors. Hydrogen atoms of the water molecules were refined isotropically with all data and the distance O-H were kept fixed at 0.95 A until the end of the multipolar refinement. The inspection of the residual Fourier maps has revealed anharmonic thermal motion features around the Ca2+ cation. Therefore, the coefficients up to order 6 of the Gram-Charlier expansion [15] were refined for the calcium cation in the scolecite. 

Fig. 2 A 1. 8-A resolution sigma-weighted (IFg-Fc) map of the octapeptide, contoured at la level. B Stereo view of the superimposed positions of the peptide [80] and carbohydrate [82] ligands. Atom types are the same as in Fig. 1. The ordered solvent (water) molecules (S) associated with the peptide complex are also shown. The solvent molecules S2, S9 and Si and the residue Rha C are shown to occupy a similar area of the site, the deep pocket of the combining site groove (see also Fig. 1). Reproduced from [80]. 2003 by The National Academy of Sciences of the USA...

In recent years, several initiatives have been launched to establish or strengthen surveillance systems, both in EU member states and at an international level, to monitor the presence of these residues in environmental matrices. When implementing measures, water bodies relevant for drinking water should receive priority. Furthermore, research is required to determine whether observations made from regional sample sets are representative of environmental concentrations nationwide [3], being essential to perform contamination maps and implement surveillance models, needed for the establishment of a sustainable strategy, to minimize environmental impact of medicines. 

---