The design of two apparati to measure solid-liquid and liquid-liquid equilibria data.
MetadataShow full item record
Two new apparati have been developed to measure solid-liquid and liquid-liquid equilibria via a synthetic visual method by determination of thermal signatures. One apparatus adopts a technique of using Peltier modules for cooling, and the other is a well-known design that uses a cryogenic fluid in a thermostatted glass cell for cooling of the sample. The Peltier design is for small sample volumes, with a 10 cm3 aluminium equilibrium cell and has a minimum operating temperature of 253.15 K. The glass design is developed to complement the Peltier and has a larger volume of 140 cm3 and a minimum operating temperature of 223.15 K. Both apparati have been semi-automated in order to increase the accuracy and improve the efficiency of data measurements. Therefore the experimenter no longer has to wait for many hours for the determination of equilibrium. This was done by incorporating software, which was specially designed for the apparati using Labview8TM, for controlling the cooling and heating rates. The uncertainty of the temperature measurements was found to be ±0.03 K for the Peltier apparatus and ±0.02 K for the Glass apparatus. Liquid-liquid equilibria data has also been measured on the Peltier apparatus, to demonstrate its versatility. This was done using a digital camera, controlled through the Labview software to identify cloud points. The results have been found to be comparable with literature values. For solid-liquid equilibria new systems of n-alkyl carboxylic acid binary mixtures have also been measured: heptanoic acid + butyric acid and heptanoic acid + hexanoic acid. These systems were measured using both apparati and both systems exhibited eutectic behaviour. All eutectic temperatures were measured on the Glass apparatus. Experimental data for these systems was modelled using the local composition models: Wilson, NRTL and UNIQUAC models. The NRTL model was found to give the best results for both systems with root mean square deviations (RMSD) of 2.16 K and 1.27 K and absolute average deviations (AAD) of 0.61 K and 0.49 K, between temperature measurements of this work and those calculated from the models, for the heptanoic acid + butyric acid and heptanoic acid + hexanoic acid systems, respectively.
Showing items related by title, author, creator and subject.
Thermodynamics of liquid mixtures : experimental and theoretical studies on the thermochemical and volumetric behaviour of some liquids and liquid mixtures. Govender, Ursula Penelope. (1996)The excess molar volumes VEm and the excess molar enthalpies HEm have been determined for several binary systems at 298.15 K using an Anton Paar Digital Densitometer and a 2277 Thermal Activity Monitor, respectively. VEm ...
Development of a dynamic still for measuring low pressure vapour-liquid-liquid equilibria : systems of partial liquid miscibility. Ndlovu, Mkhokheli. (2005)The dynamic still originally designed by Raal (Raal and Muhlbauer ) has been transformed into a valuable still that can now be used for measuring both low pressure vapour-liquid equilibria (VLE) for systems that are ...
Infinite dilution activity coefficient measurements of organic solutes in fluorinated ionic liquids by gas-liquid chromatography and the inert gas stripping method Tumba, Armel Kaniki. (2009)Environmental and safety concerns have prompted an active quest for ―green‖ alternatives to