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(Solid + liquid) phase equilibrium (SLE) has been measured for 4-chloro-2-benzofuran-1,3-dione anhydride and 5-chloro-2-benzofuran-1,3-dione anhydride using differential scanning calorimetry (DSC) over the whole concentration range. It was found that this system is a simple eutectic system. The eutectic point is at T = 336.95 K and a mole fraction of 4-chloro-2-benzofuran-1,3-dione of 0.3482. Furthermore, the results obtained in mixtures of (4-chloro-2-benzofuran-1,3-dione and 5-chloro-2-benzofuran-1,3-dione) have been compared with those predicted by the ideal model and correlated by Wilson and nonrandom two-liquid (NRTL) equations. The best modeling results were obtained using the NRTL model with the average root-mean-square deviation of σ = 7.88 K.

In this investigation, the mutual solubilities for the ternary o-nitrobenzoic acid + m-nitrobenzoic acid + ethanol system were measured at (273.15, 283.15, and 293.15) K, respectively. The isothermal phase diagrams of the system were constructed on the basis of the measured solubilities. Two solid phases were formed and confirmed by the Schreinemakers wet residue method, and the two were identified as o-nitrobenzoic acid and m-nitrobenzoic acid. The solubility fields of two solid phases were observed from the phase diagram. The phase diagrams of the ternary system are similar at the different temperatures. The crystallization regions of 2-nitrobenzoic acid and 3-nitrobenzoic acid increase as the temperature decreases. The solubility data and the ternary phase diagram can provide the fundamental basis for separation of the mixture of isomeric nitrobenzoic acids.

The solid-liquid phase equilibrium and mutual solubility for the ternary 3-chlorophthalic acid + 4-chlorophthalic acid + water system were determined at (283.15 and 313.15) K. The phase diagrams of the system were constructed on the basis of the measured solubility. The solid phases formed in the studied system were confirmed by Schreinemaker's method of wet residues. At (283.15 and 313.15) K, both 3-chlorophthalic acid and 4-chlorophthalic acid were formed in the ternary 3-chlorophthalic acid + 4-chlorophthalic acid + water system. Besides, an adductive compound with the formula (3-C6H3Cl(COOH)2 ·4- C6H3Cl(COOH)2) existed. The crystallization field of 3-chlorophthalic acid was larger than that of the adduct or 4-chlorophthalic acid at each studied temperature. The solubility data and the ternary phase diagram for the system of 3-chlorophthalic acid + 4-chlorophthalic acid + water at (283.15 and 313.15) K can provide the fundamental basis for the preparation of 3-chlorophthalic anhydride from 3-chlorophthalic anhydride and 4-chlorophthalic anhydride mixtures. valuable compounds. 1 The isomeric mixtures of these com- pounds are formed by several synthetic methods, in various proportions of 3- and 4-chlorophthalic anhydrides. 2-6 In particular, the commercial product of 3-chlorophthalic anhydride is, at present, obtained via reduced pressure distillation from the isomeric mixture of 3- and 4-chlorophthalic anhydrides. 7,8 However, the energy consumption of the distillation process is very high. Thus, crystallization is proposed as a separation method due to its low energy consumption and the possibility of obtaining products with higher purity than that achieved by other conventional separation operations. Hence, it is possible to separate 3-chlorophthalic acid and 4-chlorophthalic acid mixtures via crystallization using water as a solvent, since the solubility of 3-chlorophthalic acid in water was much less than that of 4-chlorophthalic acid. 9 During the crystallization separa- tion process, the optimization of process conditions is closely related to the solubility of 3-chlorophthalic acid and 4-chlo- rophthalic acid in water. Therefore, it is important to study the system and construct the phase diagram of the ternary 3-chlo- rophthalic acid + 4-chlorophthalic acid + water system for improving the separation process. It is well-known that solid-liquid phase equilibrium data are important in crystallization processes. Although the solubility of the binary systems of 3-chlorophthalic acid + water and 4-chlorophthalic acid + water has been determined and the corresponding binary phase diagrams constructed, 9 to the best of our knowledge, no investigations on the solubility or phase diagram for the ternary 3-chlorophthalic acid + 4-chlorophthalic acid + water system have been made. The objective of this research is to investigate and generate the phase diagrams of the ternary system at (283.15 and 313.15) K by Schreinemaker's method of wet residues which demonstrates the temperature dependence of the ternary phase diagram. 10-13 In a ternary system involving at least one solid and one liquid phase, the composition of the solid phase is often determined indirectly, to avoid separation crystals and the complete removal of the adhering mother liquor from them. Extrapolation is made by Schreinemaker's method of wet residues, based on the following: The tie line joining the composition of the pure solid and the saturated liquid in equilibrium with it is the locus of all intermediate compositions corresponding to varying amounts of solid and liquid phases. This includes the composition of the liquid phase and crystals wet with mother liquor. A straight line drawn through a pair of points representing such composi- tions on a phase diagram is a segment of the tie line and therefore passes through the composition of the pure solid. The lines drawn through several such pairs of composition, each corresponding to a different original mixture, have a common intersection at the composition of the pure solid phase. The composition of the common intersection is in agreement with direct analysis obtained by crystallization.

The solubility of 3-chlorophthalic anhydride and 4-chlorophthalic anhydride in ethyl acetate, acetone, and 1,4-dioxane and the solubility of 3-chlorophthalic acid and 4-chlorophthalic acid in water were measured using Schreinemaker’s wet residue method at temperatures ranging from (283.15 to 333.15) K at atmospheric pressure. Results of these measurements were correlated with the modified Apelblat equation.

A compact and simple ultra-wideband microstrip-fed planar antenna with double bandstop characteristic is presented. The antenna consists of a rectangular monopole and two W-shaped slots inserted into the radiating patch and the truncated ground plane. By using a W-shaped slot defected ground structure (DGS) in the feedline, a stopband of 800 MHz (from 5.1 to 5.9 GHz) for band rejection of wireless local area network (WLAN) is achieved. To obtain the other stopband (from 3.7-4.4 GHz), a same shaped slot is etched into the monopole. Moreover, the two stopbands can be controlled by adjusting the length of the slot respectively. The simulation results show that the designed antenna, with a compact size of 38.5 mm×42.5 mm, has an impedance bandwidth of 2.811 GHz for voltage standing wave ratio (VSWR) less than 2, besides two frequency stopbands of 3.74.4 GHz and 5.15.9 GHz. Moreover, the main features including omnidirectional H-plane radiation patterns and the appropriate impedance characteristic are achieved by beveling the radiating patch and the microstrip-fed line of the proposed antenna.