Iranian Journal of Chemistry and Chemical Engineering
Volume:11 Issue: 2, Nov-Dec 1992

Polymerization rates of silica at various concentrations and pHs have been studied via nephelometry. The ability and potency of ultrasonic radiation on the coagulation process in aqueous samples with and without silica colloidal particles have been extensively investigated. Factors affecting the rate and filtration volume such as silica concentration, time of radiation, temperature, and frequency of radiation have also been studied. The results indicate that ultrasonic radiation has a two folded effect: on the one hand it breaks down the large flocs and on the other it results in the flocculation of small particles. The above mentioned effects lead to a reduced uniformity coefficient for the filter beds made of such coagulated particles.

Transformation of 3-propargylmercapto-6 methyl-1, 2, 4- triazin – 5 (2H0 – one (1; R=CH3) to 3, 6- dimethyl – 7H – thiazolo [3, 2-b] [1,2,4] triazin – 7 – one (2) is performed under basic condition. The formation of (2) may be mainly due to the high reactivity of acetylenes towards nucleotides and isometization of the intermediate.

The interaction between hydronium ion and several crown ethers was studies via conductometry in nitromethane at 25°C and 1H-NMR techniques. The stabilities of the resulting 1:1 complexes were determined from the conductance data and found to vary in the order DC18C6>18C6>DB30C10>DB24C8>DB18C6>~B15C5>DB21C7. For the first time, evidences for the formation of a 2:1 sandwich complex between the smaller crown ethers (i.e.B15C5 and 18-crowns) and bydronium ion in solution were observed by monitoring the molar conductance of bydronium ion as a function of the ligand to cation mole ratio. The 1H-NMR data support the existence of such 2:1 adduct in solution.

Formation equilibria of dioxy vanadium (V) Complex with alanine in acidic media (pH<2.3) has ben investigated potentiometrically and spectrophotometrically. In this condition the 1:1 complex has the formula VO2Y, where Y- represents the fully dissociated aminocarboxylate anion. The stability constant of VO2Y was determined as at and I=1 mol per liter of sodium perchlorate. The protonation constant of alanine was also determined potentiometrically under above condition.

Accurate vapor – liquid equilibrium data have been obtained for ethyl acetate + 2-propanol and ethyl acetate + ethanol midtures at 84.8 kPa, and the results are discussed thermodynamically. The vaporliquid equilibrium data are correlated with Redich – Kister, Margules, Van-Laarand Ortega, Equations the parameters and standard deviation of which are calculated and reported. The best correlation is found in the case of the Ortega’s equation.

The GC of halides (chloride, bromide and iodide) using phenylboronic acid (PBA), 4 – bromophenylboronic acid (BPBA), 3, 5 bis (trifluoromethyl) phenylbronic acid (FPBA) and 2,4 – dichlorophenylboronic acid (CPBA) as derivatizing reagents are compared. The reactions are carried out in the presence of mercuric salts. The detection systems used are FID and ECD. The thermal analysis of the compounds are studied prior to GC to get an indication of the likely operating temperatures. The unsubstituted phenylboronic acid show better volatility and FID response, but substituted phenylboronic acids exhibit better responses using ECD system. Finally FPBA is examined for the possible use in quantitative determination of chloride, bromide and iodide using solvent extraction procedure and ECD detection system. Detection limits for chloride, bromide and iodide are reported in the range of 0.29-0.35 pg.

Based on Gibbs-Duhem law and using UNIFAX-FV computer algorithm, the activity of polymer component in polymer-sovent systems is determined. The variation of activity of components with concentration at different temperatures are used to find the equilibrium concentrations, UCST, and LCST for the systems. Also by generalization of the method, Gel-Liquid equilibrium is studied in some three component systems: polymer-solvent-solvent.

A correlation based on the general form of cubic equation of state has been derived. This equation provides a convenient mathematical form of the Joule – Thomson coefficient in terms of the state variables V and T. The Joule – Thomson coefficient calculated by this correlation has been compared with experimental data. It has been shown that the Redilich – Kwang equation of state is a suitable equation for prediction of Joule – Thomson coefficient of non-hydrocarbon compounds. The Joule – Thomson coefficient of light hydrocarbons can be obtained with greater accuracy through the use of the Soave – Redlich – Kwang equation of state. As hydrocarbon compounds become heavier the Joule – Thomson coefficient correlation based on the Peng – Robinson equation of state givesmore accurate results. In the superheat region and for simple and quantum compounds the Redlich – Kwang equation of state is superior. Because of the complexity of the Joule – Thomson coefficient the correlation obtained by the Lee-Kessler equation of state and based on the high average percent error resulting from this correlation, the Lee-Kessler equation of state is not recommended for prediction of the Joule-Thomson coefficient.