Thermodynamics of ionic-association in aqueous solutions of Ca and Mg organic salts using ion-selective electrode technique—II. benzoate, o-toloate, o-chlorobenzoate and salycylate

The stoichiometric association constants, K, the thermodynamic association constant, K_A, and the other thermodynamic parameters such as ΔS°, ΔH° and ΔG° for the association between each of the Ca and Mg ions with benzoate, o-toloate, o-chlorobenzoate and salycylate have been determined at 25°C, 35°C and 45°C in aqueous media. Ion-selective electrode technique has been used in the measurements of Ca and Mg ion activitiesThe trend of association behavior of both Ca and Mg aromatic salts could not be explained on the basis of pK_a of the mother organic acids but could be explained based on the trend of Hammet function σ of these salts themselves relative to the corresponding benzoate salt.     

Design for the Future: Educational Institutions in the Gulf

Despite a distinguished heritage of learning in the Middle East, the expansion of provision for higher education is currently at an unprecedented scale. The Gulf States, in particular, are seeking to keep up with accelerated population growth and a demographic ‘youth bulge’. Guest-Editor Kevin Mitchell describes the architectural approaches employed in the design of institutions in the region from the first universities in Saudi Arabia to Foster + Partners's ground-breaking sustainable design for the Masdar Institute in Abu Dhabi and future projects.     

Thermodynamics of ionic-association in aqueous solutions of Ca and Mg organic salts using ion-selective electrode technique—I. Formates, acetates, propionates and butyrates

The divalent selective electrode together with high precision solid state, digital pH -mv -meter makes broader application of potentiometry in physical and inorganic chemistry a certainty. The above set-up is used to determine the stoichiometric constants, K, for Ca and Mg ions association with formates, acetates, propionates and butyrates at 25°, 35° and 45°C in aqueous media. The K-values were converted to infinite dilution K_A values were found to be 8.4 LM⁻¹, 10.4 LM⁻¹, 19.1 LM⁻¹ and 19.3 LM⁻¹ for calcium salts of formate, acetate, propionate and butyrate respectively. Also K_A values for Mg salts of formate, acetate, propionate and butyrate were found to be 7.8 LM⁻¹, 9.5 LM⁻¹, 13.1 LM⁻¹ and 13.1 LM⁻¹ respectively. Other thermodynamic parameters such as ΔG°, ΔH° and ΔS° are also obtained from the variation of K_A with temperature for each salt. The data are interpreted relative to each other on basis of pK_a of the corresponding organic acid. Their temperature behaviour is similar to those salts derived from strong acids such as sulphates, rather than weak acids.     

Technical and Economic Advantages of Producing and Applying Ozone At High Concentration

Today ozone can be produced in concentrations up to 3.5 wtJ (12 g/Nm³) in air and 7 wt% (92 g/Nm³) in oxygen with simultaneously low specific energy consumption. The high concentrations improve the transfer efficiency and the reaction kinetics of ozone. This is demonstrated with reference to the design basis of the water treatment plants of Los Angeles, Dordrecht and Jeddah. In all cases the overall costs per kilogram of ozone are minimized by choosing the appropriate ozone concentration between 2 wt% (24 g/Nm³) and 6 wt% (79 g/Nm³).     

Preliminary Assessment of Water Quality along the Red Sea Coast near Jeddah,Saudi Arabia

Abstract

This paper presents the results of preliminary assessment of water quality along Red Sea coast adjoining Jeddah, Saudi Arabia. Jeddah is a major city with a population of over 2.6 million and an area 1,200 km^2.. To study the impacts, samples of the Red Sea were collected from 24 important locations near Jeddah and analyzed in the laboratory for various water quality parameters. These parameters included: biological oxygen demand (BOD), chemical oxygen demand (COD), phosphorus, dissolved oxygen, ammonia nitrogen, nitrates, sulfates, total alkalinity, chlorides, and pH. The results of the study show considerable variations in water quality depending upon the location along the Red Sea coast. The BOD values in the sea water are negligible except in the Balad downtown lake near treatment plant where the values are quite high ranging from 51 to 812 mg/l. Here, the total phosphorus is also high with value of 3.81 mg/l. Dissolved oxygen values along the coast vary from 2.5 to 6.4 mg/l. The variations in nitrate concentration in the Red Sea water along the coast are observed to range from 6.90 to 26.61 mg/l. This study provides a preliminary assessment of the coastal pollution and will act as a data base for future investigations and monitoring of the Red Sea coastal waters.     

Malathion exposed seeds of Vigna Sinensis

Plasma membrane bound ATPase of Vigna sinensis (L) is activated by Mg⁺² and is further stimulated by monovalent cations like Na⁺/K⁺, at a definite pH and substrate concentration. The true substrate for the enzyme was Mg⁺⁺‐ATP. Ca⁺⁺ cannot replace Mg⁺⁺ so far as the activation of this enzyme is concerned. Activation does not alter much when treated with ouabain. These results support the concept that cation transport at the plasma membrane of root cells of Vigna sinensis (L) is coupled to a cation‐activated ATPase. Malathion (O, O‐dimethyl phosphorodithioate of diethyl mercapto succinate), an organo phosphorus insecticide, activates these enzymes at a concentration of 400 ppm. This increase in activity may be associated with some alteration in the membrane structure, and stimulation by malathion has been found to be of non‐competitive in nature when the divalent and monovalent ions are included in the system.     

The Evolution of Tall Building in the Gulf: From the Sensational to the Sensitive

In just 35 years the built environment in the Gulf region has evolved so rapidly that it has gone from having no high-rise buildings to having the world's tallest building — SOM's Burj Khalifa in Dubai. Terri Meyer Boake , a professor at the University of Waterloo in Ontario and specialist in steel construction and skyscraper design, provides an overview of the fast-paced development of this building typology.     

Designing sustainable landfill for Jeddah City, Saudi Arabia

 For the last 12 years the solid waste of Jeddah City has been placed in Wadi Nakhil, to the east of the city. This facility is now 80% full. No geotechnical site characterisation was undertaken prior to opening this municipal landfill site in 1982 and, being so close to the city, it now poses risks to the health of nearby residents as well as ecological dangers. The paper considers the requirements of a new site and discusses the most appropriate method of closing the existing site to ensure its long-term safety. Received: 28 August 1998 · Accepted: 30 August 1999     

Comparative study of the geotechnical properties of the coastal Sabkhas of Saudi Arabia and their hazardous effects

Sabkha is composed of sand deposits mixed with silt and clay intercalated with evaporites. Two types of sabkha are present in Saudi Arabia: the inland sabka, which is found in the northern part of the country and coastal sabkha, which is located along the Red Sea and Arabian Gulf. The main geotechnical hazards include settlement, corrosive action, heave due to salt crystallization/recrystallization and flooding due to the low infiltration rates. This comparative study indicates the engineering properties of the coastal sabkha along the Red Sea differ from those of the sabkha along the Arabian Gulf, which is likely to be more costly to develop.     

Drawing on Sand: Cities in the Making

Steven Velegrinis , Director of Urban Design for Perkins+Will in Dubai, and Guest-Editor George Katodrytis liken Gulf cities to the shifting sands that they sit upon. Showing urban development to be in a constant state of flux in the region, they highlight four key eras in the unprecedented rapid development of these cities.