LIQUID DIFFUSION COEFFICIENT APPARATUS - CER MEASUREMENT AND INSTRUCTIONAL CAPABILITIES ‘This laboratory equipment has been designed to enable measurement of ‘molecular diffusivities and, in so doing, to familiarise students with the basic > Accurate measurement of mass transfer rates in the absence of convective effects > Use ofFick’s Law to deduce diffusion coefficients from measurements ‘of mass transfer rate and concentration difference > Simple analysis ofa frst order unsteady state process effect of concentration notions of mass transfer theory on diffusion coefficients ‘The liquid elifusiviy apparatus (CERD) relates > Gaining familiarity with the use of laboratory instruments to achieve accurate per tterctaceatr eee eras measurements of data required for industrial process design > Windows data logging software included Ga 9 150 901708 he atest veson af theta sheet avalable atDISCOWER im DESCRIPTION ‘Armfield has developed a unique diffusion cell which ‘overcomes the traditional problem of slow diffusion rates in liquids requiring long observation times, but without sacrificing accuracy or introducing convective effects. Essentially, the cell consists of a honeycomb of accurately dimensioned capillaries positioned between two liquids of differing concentration of the solute, whose diffusion coefficient is to be determined. In practice, a small volume of concentrated solution is placed on one side of the honeycomb, whilst the other side consists initially of a large volume of pure solvent (water). As diffusion of the solute occurs, the concentration within the larger volume increases, and. is monitored with a conductivity sensor and meter. The mixture is continuously stirred with a magnetic stirrer to ensure uniform concentration within the bulk liquid. Whilst the conductivity sensor may be readily calibrated for any required aqueous system, for introductory studies dilute solutions of sodium chloride are recommended, for which conductivity data is provided. ‘TECHNICAL DETAILS Diffuser vessel: Capacity 11 Conductivity meter: 3 ranges 199.9p5 t019.99mS Computer output: R5232 RECOMMENDED ACCESSORIES Stop clock Cartridge deioniser REQUIREMENTS Electricity supply: Battery operated Data logging requires a customer supplied PC, with S232 Serial interface, running Windows 98 or later. COMPLEMENTARY PRODUCTS CERa Mkil: Gaseous Diffusion Coefficient Apparatus ES: Wetted Wall Gas Absorption Column UOP3BM: Batch Distillation Column UOP3CC: Computer interfaced Distillation Column UOPAMIII: Solid-Liquid Extraction Unit OPS: —_Liquid-Liquid Extraction Unit UOP7: Gas Absorption Column wo noraom enamel ae SG. ORDERING SPECIFICATION + Bench mounted apparatus for the determination of diffusion coefficients of components in the liquid phase. The method employs a diffusion cell of capillary tubes so constructed to permit eq ‘molar counter diffusion between liquids of differing concentration each side of the cell without convective effects being present + Concentration changes on one side of the cell with respect to time are measured with the conductivity cell and the meter provided anda magnetic ster keeps the bulk solution well mixed + Possible to obtain reproducible and accurate values of diffusivity Within a period of 1.5 hours of practical laboratory time + Battery powered - EXPERIMENTAL CAPABILITIES > Accurate measurement of mass transfer rates inthe absence of convective effects. > Use of gas laws to calculate concentration, differences in terms of partial pressures. > Use of Fick's Law to deduce diffusion coefficients from measurement of mass transfer rate and ‘concentration difference, > Simple analysis ofa first order unsteady state process > Effect of concentration on diffusion coefficients > Gaining familiarity with the use of laboratory Instruments to achieve accurate measurements of data required for industrial process design + Software is included to enable the temperature and conductivity in the diffusion vessel to be displayed, logged and recorded ‘on a customer supplied PC, using an RS232 interface OVERALL DIMENSIONS / NET WEIGHT Height: 031m Diameter: 0.19m Conductivity Meter Height: 013m Width: 015m Depth: 025m SHIPPING SPECIFICATION Volume: o.10m? Gross Weight: 10kg San OR eode osu we www.armfield/co.uk