Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Vapor-liquid equilibrium is paramount in engineering applications such as distillation, environmental modeling, and general process design. Understanding the interactions of components in a mixture is very important in designing, operating and analyzing such separators. The activity coefficient is an excellent tool for relating molecular interactions to mixture composition. Finding the molecular interaction parameters allows future prediction of the activity coefficients for a mixture using a model.
Vapor-liquid equilibrium is a critical factor in common processes in the chemical industry, such as distillation. Distillation is the process of separating liquids by their boiling point. A liquid mixture is fed into a distillation unit or column, then boiled. Vapor-liquid equilibrium data is useful for determining how liquid mixtures will separate. Because the liquids have different boiling points, one liquid will boil into a vapor and rise in the column, while the other will stay as a liquid and drain through the unit. The process is very important in a variety of industries.
In this experiment, the activity coefficients of mixtures of various com…
1Chemical Sensing & Fuel Technology, Chemistry Division, U.S. Naval Research Laboratory, 2NOVA Research, Inc., 3Bio/Analytical Chemistry, Chemistry Division, U.S. Naval Research Laboratory, 4Navy Technology Center for Safety and Survivability, Chemistry Division, U.S. Naval Research Laboratory
1School of Chemistry and Biochemistry, Georgia Institute of Technology, 2Earth-Life Science Institute, Tokyo Institute of Technology, 3Institute for Advanced Study, 4Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, 5Goddard Center for Astrobiology, NASA Goddard Space Flight Center, 6Geosciences Research Division, Scripps Institution of Oceanography, University of California at San Diego
Source: Laboratory of Dr. Nicholas Leadbeater — University of Connecticut
Distillation is perhaps the most common laboratory technique employed by chemists for the purification of organic liquids. Compounds in a mixture with different boiling points separate into individual components when the mixture is carefully distilled. The two main types of distillation are "simple distillation" and "fractional distillation", and both are widely used in organic chemistry laboratories.
Simple distillation is used when the liquid is (a) relatively pure (containing no more than 10% liquid contaminants), (b) has a non-volatile component, such as a solid contaminant, or (c) is mixed with another liquid with a boiling point that differs by at least 25 °C. Fractional distillation is used when separating mixtures of liquids whose boiling points are more similar (separated by less than 25 °C).
This video will detail the fractional distillation of a mixture of two common organic solvents, cyclohexane and toluene.…
1Department of Mechanical & Aerospace Engineering, University of Missouri
1Wellness Promotion Science Center, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 2Advanced Research Center for Human Sciences, Waseda University, 3Department of Clinical Laboratory Science, Graduate School of Medical Science, Kanazawa University, 4Asanogawa General Hospital
1McKetta Department of Chemical Engineering, The University of Texas at Austin
1Institute of Materials, Ecole Polytechnique Fédérale de Lausanne (EPFL), 2Colloid Chemistry Department, Max Planck Institute of Colloids and Interfaces
Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry
All chemical reactions have a specific rate defining the progress of reactants going to products. This rate can be influenced by temperature, concentration, and the physical properties of the reactants. The rate also includes the intermediates and transition states that are formed but are neither the reactant nor the product. The rate law defines the role of each reactant in a reaction and can be used to mathematically model the time required for a reaction to proceed. The general form of a rate equation is shown below:
where A and B are concentrations of different molecular species, m and n are reaction orders, and k is the rate constant. The rate of nearly every reaction changes over time as reactants are depleted, making effective collisions less likely to occur. The rate constant, however, is fixed for any single reaction at a given temperature. The reaction order illustrates the number of molecular species involved in a reaction. It is very important to know the rate law, including rate constant and reaction order, which can only be deter…
1The Ritchie Centre, Monash Institute of Medical Research, 2Department of Obstetrics and Gynaecology, Monash Medical Centre, 3Animal Resource Centre, Perth, Australia, 4Wake Forest Institute for Regenerative Medicine
Source: Hsin-Chun Chiu and Tyler J. Morin, laboratory of Dr. Ian Tonks—University of Minnesota Twin Cities
Schlenk lines and high vacuum lines are both used to exclude moisture and oxygen from reactions by running reactions under a slight overpressure of inert gas (usually N2 or Ar) or under vacuum. Vacuum transfer has been developed as a method separate solvents (other volatile reagents) from drying agents (or other nonvolatile agents) and dispense them to reaction or storage vessels while maintaining an air-free environment. Similar to thermal distillations, vacuum transfer separates solvents by vaporizing and condensing them in another receiving vessel; however, vacuum transfers utilize the low pressure in the manifolds of Schlenk and high vacuum lines to lower boiling points to room temperature or below, allowing for cryogenic distillations. This technique can provide a safer alternative to thermal distillation for the collection of air- and moisture-free solvents. After the vacuum transfer, the water content of the collected solvent can be tested quantitatively by Karl Fischer titration, qualitatively by titration with a Na/Ph2CO solution, or by 1H NMR spectroscopy.…
1Institute of Biology / Geobotany and Botanical Garden, Martin-Luther-University Halle-Wittenberg, 2German Centre for Integrative Biodiversity Research
1USDA-ARS, Grassland Soil and Water Research Laboratory, 2Department of Integrative Biology, University of Texas at Austin
1Division of Chemistry and Chemical Engineering, California Institute of Technology, 2Joint Center for Artificial Photosynthesis, California Institute of Technology, 3Advanced Light Source, Lawrence Berkeley National Laboratory, 4Beckman Institute, California Institute of Technology
1Physical Sciences Division, Pacific Northwest National Laboratory
Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Surface area and pore size distribution are attributes used by adsorbent and catalyst manufacturers and users to ensure quality control and to determine when products are at the end of their useful lives. The surface area of a porous solid is directly related to its adsorption capacity or catalytic activity. The pore size distribution of an adsorbent or catalyst is controlled such that pores are large enough to easily admit molecules of interest, but small enough to provide a high surface area per mass.
Surface area and pore size distribution can be measured by the technique of isothermal nitrogen adsorption/desorption. In this experiment, a nitrogen porosimeter will be used to measure the surface area and pore size distribution of a silica/alumina powder.…
1Department of Chemistry, Universität Konstanz
1Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, 2Department of Behavioral Neuroscience, Oregon Health & Science University
1Department of Chemical Engineering, Imperial College London
1Department of Chemistry, New York City College of Technology, City University of New York (CUNY)
1Department of Chemistry, Boston University, 2Department of Biomedical Engineering, Boston University, 3Department of Medicine, Boston University
1Applied Water Physics, Wetsus - Centre of Excellence for Sustainable Water Technology, 2IRCAM GmbH, 3Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology
1Marcoule Institute for Separative Chemistry, UMR 5257 CEA-CNRS-UM2-ENSCM
1Department of Chemistry, Institute of Organic Chemistry, Bielefeld University
1Division of Pulmonary Medicine, University of Alberta, 2Faculty of Physical Education and Recreation, University of Alberta, 3Divisions of Critical Care and Cardiology, University of Alberta, 4Faculty of Rehabilitation Medicine, University of Alberta, 5G.F. MacDonald Centre for Lung Health
1Molecular Microbial Biochemistry Laboratory, Faculty of Science (Applied Bioscience Program), University of Ontario Institute of Technology
1Department of Chemistry & Biochemistry, The Biodesign Institute – Center for Personalized Diagnostics, Arizona State University
Source: Robert M. Rioux & Taslima A. Zaman, Pennsylvania State University, University Park, PA
While the use of various chemicals in experimental research is essential, it is also important to safely store and maintain them as a part of the Environmental, Health and Safety (EHS) program. The properties of chemicals and their reactivity vary broadly and if chemicals are not managed, stored, and labeled properly, they can have harmful or even destructive consequences such as toxic fume production, fire or explosion, which may result in human fatality, property damage or environmental hazards. Therefore, an appropriate chemical label should identify the material and list the associated hazards, and users should have knowledge of how to read chemical labels and safety data sheets (SDS). Proper chemical storage must meet OSHA (Occupational Safety and Health Association) standards and this can prevent most chemical reactivity hazards.…
1Unit of Anatomy, Department of Medicine, University of Fribourg