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Chapter

Cover Interfacial Science

The liquid–liquid interface: emulsions; membranes  

This chapter talks about interest in the liquid-liquid interface that is concerned with the topic of emulsions, which is closely related to the study of food science. It explains that the liquid-liquid interface consists of liquid drops dispersed in another liquid, which are normally thermodynamically unstable and are usually stabilized by the adsorption of an emulsifier. It also considers the movement of a solute from one liquid phase to another. This is important with processes such as liquid-liquid extraction in the chemical industry and in many biological situations. The chapter highlights the role of membranes that can be significant in solute transport and is an essential feature of many biological processes. It reviews emulsions that are concerned with water or an aqueous solution as one phase and a water-insoluble organic liquid as the other phase.

Chapter

Cover Atkins’ Physical Chemistry

Liquids  

This chapter describes substances that are liquids under normal conditions and chemical reactions that take place in liquids. It emphasizes the importance of being able to describe and understand the structure of the liquid phase and the interface with its vapour. It also looks at the properties of liquids that reflect the short-range order of their molecules in the bulk and the behaviour of their molecules at the mobile surface. The chapter discusses how molecules attract each other when they are less than a few diameters apart but repel each other as soon as they come into contact. It explains that attraction is responsible for the formation of condensed phases and the repulsion is responsible for the fact that liquids have a definite bulk.

Chapter

Cover Atkins’ Physical Chemistry

Phase diagrams of binary systems: liquids  

This chapter focuses on phase diagrams of systems of liquids. It begins by looking at vapour pressure diagrams. The partial vapour pressures of the components of an ideal mixture of two volatile liquids are related to its composition by Raoult's law. The chapter then considers temperature–composition diagrams, in which the boundaries show the composition of the phases that are in equilibrium at various temperatures. The lever rule is used to deduce the relative abundances of each phase in equilibrium. The chapter also discusses how the separation of a liquid mixture by fractional distillation involves repeated cycles of boiling and condensation. An azeotrope is a liquid mixture that boils without change of composition. Finally, the chapter examines liquid–liquid phase diagrams.

Chapter

Cover Elements of Physical Chemistry

Phase diagrams of mixtures  

This chapter details the phase diagrams of mixtures. The equilibria between phases (at constant pressure) are represented by lines on a temperature–composition diagram. The chapter begins by looking at the phase diagram of a binary mixture of two volatile liquids. This kind of system is important for understanding fractional distillation, which is a widely used technique in industry and the laboratory. The chapter then considers liquid–liquid phase diagrams, as well as liquid–solid phase diagrams. It differentiates between an azeotrope mixture and a eutectic mixture, and explains the lever rule and the technique of zone refining. Finally, the chapter examines the Nernst distribution law, which states that, in an ideal system, the ratio of mole fractions in the two phases is independent of the total amount of solute.

Chapter

Cover Interfacial Science

The gas-liquid interface: adsorption; films and foams; aerosols  

This chapter describes some of the most obvious and dramatic effects of adsorption that can be seen at the air-solution interface. It talks about liquid drops that change their shape, foams that can be formed on liquids that otherwise will not foam, and the rise of liquids in capillaries that is reduced. It also analyses the enhanced spreading of liquids over solid surfaces, the reduction of the ability of light winds to ruffle the surface of water in a pond, and soils that are wetted more readily by water. The chapter deals with the measurement of adsorption by analysis of the surface or by change in bulk phase concentration that is usually not feasible as the area of a gas-liquid interface is usually small and sample collection is often difficult. It explains how adsorption is normally determined from surface tension data using the Gibbs equation.

Chapter

Cover Interfacial Science

The liquid–solid interface: adsorption; colloids  

This chapter discusses the removal of unwanted impurities from a liquid by passage through a column of a solid adsorbent. It explores the separation of different solutes by column chromatography, high performance liquid chromatography, and paper chromatography, which are all examples of the adsorption of solutes at the liquid-solid interface. It also analyses the sols as examples of solid-liquid interfaces, which are dispersions of solid colloidal particles in a liquid. The chapter demonstrates how clay minerals interact readily with water and dissolved ions, and some of them swell, generating considerable expansion pressures. It talks about clay minerals when mixed with water, which have important industrial applications, such as for making bricks and tiles, pottery and ceramics, and drilling muds.

Chapter

Cover Non-Aqueous Solvents

General properties  

This chapter focuses on the importance of non-aqueous liquids in living systems, and states that water is considered the most abundant liquid on earth. It examines the range of liquid solvents available and discusses how the choice of solvents is related to the various solvent properties. It also explains that solvents are used to bring reactants together at suitable concentrations, such as endothermic reactions wherein heat can be supplied readily by heating the solvent and exothermic reactions wherein the solvent can act as a heat sink. The chapter discusses how solvents frequently react with solutes and how solutions offer a convenient way of delivering chemical compounds to their point of use. It outlines the multiple types of solvent that act as a solvent to different solutes.

Chapter

Cover Making the Transition to University Chemistry

States of Matter  

This chapter explains the states of matter. It notes how a dipole exists if a positive charge is separated from a negative charge by a distance. The bond's polarity and the shape of the molecule are needed to figure out whether polyatomic molecules have a dipole moment. The molecule's polarizability is in proportion with the induced dipole moment. The chapter also notes that intermolecular forces are forces between molecules that can be classified as dipole-dipole forces, dispersion forces, or hydrogen bonding. The chapter also looks at particles and definitions of solids, liquids, and gases. Finally, it lists the four main types of crystalline solids: simple molecular, giant covalent, ionic, and metallic.

Chapter

Cover Atkins’ Physical Chemistry

Self-assembly  

This chapter talks about aggregates of small and large molecules form the basis of many established and emerging technologies, including their structures and properties. It cites colloids and micelles, which form spontaneously by self-assembly of molecules or macromolecules and are held together by molecular interactions. It also defines self-assembly as the spontaneous formation of complex structures of molecules or macromolecules, which are held together by molecular interactions, such as Coulombic, dispersion, hydrogen bonding, and hydrophobic interactions. The chapter cites examples of self-assembly, which include the formation of liquid crystals and of protein quaternary structures from two or more polypeptide chains. It analyses the dissolution process in more detail by illustrating a hypothetical initial state in which the alcohol is present in water as individual molecules.

Chapter

Cover Atkins’ Physical Chemistry

Motion in liquids  

This chapter shows how molecular motion in liquids from is different to that that in gases on account of the presence of significant intermolecular interactions and the much higher density typical of a liquid. It explores the electrical resistance of electrolyte solutions and analyses it in terms of the response of the ions to an applied electric field. It discusses how solute molecules and ions move through liquid environments. The chapter demonstrates how ions reach a terminal velocity when the electrical force on them is balanced by the drag due to the viscosity of the solvent. It mentions inelastic neutron scattering, in which the energy neutrons collect or discard as they pass through a sample is interpreted in terms of the motion of its molecules.

Chapter

Cover Biomedical Science Practice

Chromatography  

Qiuyu Wang, Nessar Ahmed, and Chris Smith

This chapter studies chromatography, which is the collective term for a family of analytical techniques used to separate the components of mixtures of molecules for their identification and possible estimation of their concentrations in the original mixture. All chromatographic techniques are based on differences in the relative affinities of the molecules in a mixture of two different and immiscible phases, one of which is mobile and the other stationary. The basis of all forms of chromatography is the partition or distribution coefficient, which describes the way in which a substance distributes at equilibrium between two immiscible phases. Most types of chromatography are used in biomedical science laboratories to assist in analysing and purifying analytes from a variety of clinical samples. The chapter then looks at planar chromatography, column chromatography, high-performance liquid chromatography, and gas-liquid chromatography.

Chapter

Cover Process Development

Equilibria in multiphase systems  

This chapter addresses equilibria in multiphase systems. Many processes are operated under conditions where more than one phase is present. This is often due to economic considerations: when it is necessary to contact large water-insoluble reactants with inorganic reagents, reactions are frequently run with either a separate solid phase or else a solution phase containing the inorganic reagent. Workup processes frequently involve the washing of a solution of a water-insoluble product which is dissolved in an organic solvent such as toluene with water in order to remove inorganic residues. The chapter then looks at simple distribution equilibria; solubilities of ionisable substrates; liquid–liquid partition of ionisable substrates; and ternary phase diagrams.

Chapter

Cover Process Development

Dispersion and mass transfer in multi - phase systems aqueous alkali  

This chapter explores dispersion and mass transfer in multi-phase systems. Many reactions involve more than one phase, usually two, commonly three and even four or more. In order for the reaction to proceed, mass must transfer between these phases, and it is easy to overlook the fact that considerable effort may be required to distribute them well enough and promote mass transfer to a sufficient extent that the reaction can proceed at a reasonable rate. A gas bubbled through a liquid will not react at any meaningful rate unless well dispersed as small bubbles, and immiscible liquids will not react unless one is dispersed as fine droplets within the other. It is most common for fine chemical reactions to be carried out in a continuous liquid phase. The chapter then looks at phase boundary diagrams and phase inversion.

Chapter

Cover Physical Chemistry

Phase equilibrium  

This chapter discusses phase, which is a form of gas, liquid, solid, or supercritical fluid which is uniform in its chemical composition and its physical state. The chapter emphasizes that 'vapour' is used to describe the gaseous phase of substances which are liquids or solids at room temperature. The chapter also looks at 'vapour pressure', which is the equilibrium partial pressure exerted by a liquid in a sealed container at a fixed temperature. The chapter also covers the phase behaviour and phase transitions of one-component systems. The chapter includes a mention of the phase behaviour of two-component mixtures, such as the phenomena of colligative properties. It explores the term 'ideal gas', which refers to a system where the gaseous molecules experience no intermolecular forces.

Chapter

Cover Instrumental Analysis (International Edition)

Liquid Chromatography  

This chapter examines liquid chromatography (LC) and lays out the fundamental theory involved. It describes a sample in LC, which is dissolved in a solvent called the mobile phase. Then the solvent carries the sample into the stationary phase. It also details how the mobile phase flows through the stationary phase, noting the various components of the sample that are distributed between the immobile stationary phase and the flowing mobile phase. The chapter covers instrumental considerations that provide for high performance, high resolution, and the automation of modern LC. It looks at ways in which LC separations can be accomplished and determines how to take advantage of various physical and chemical characteristics to distinguish one component from another.

Chapter

Cover Atkins’ Physical Chemistry

Phase diagrams of ternary systems  

This chapter addresses how the behaviour of a system with three components is represented using a triangular phase diagram and how such diagrams are interpreted. Ternary phase diagrams are widely used in metallurgy and materials science. At a fixed temperature and pressure, the phase diagram of a ternary system is conveniently represented using a triangular graph. In a ternary system, the tie lines in the two-phase region are constructed experimentally by determining the compositions of the two phases that are in equilibrium, marking them on the diagram, and then joining them with a straight line. The chapter then looks at partially miscible liquids and ternary solids.

Chapter

Cover Interfacial Science

Capillarity and the mechanics of surfaces  

This chapter explains surface tension as a phenomena observed in systems containing an interface in which one of the phases is a liquid. It refers to the rise of liquid in a narrow tube as an example of surface tension, which is characterized by the drops of liquid tending to be spherical and the water spreading evenly on some surfaces. It also reviews the origin of surface tension from a molecular point of view, which considers the forces acting on a molecule at the surface of a liquid compared to those acting on one in the bulk. The chapter analyses the methods for measuring the surface tensions of solids that are at best approximate and often involve questionable assumptions. It highlights an example wherein the measured increase in vapour pressure for small spherical particles of solid can be used with the Kelvin equation.

Chapter

Cover Interfacial Science

Insoluble monolayers and Langmuir-Blodgett films  

This chapter reviews the adsorption at the gas-liquid interface of amphiphiles whose hydrophilic-lipophilic balance made them soluble in water. It discusses adsorbed films substances that have significant dynamic and equilibrium relationships with one of the bulk phases, noting that much information about the adsorbed films can be obtained from these relationships and from measurements on the bulk phase. It also examines amphiphiles with a stronger lipophilic or hydrophobic moiety that are less soluble in water and in the extreme are practically insoluble. The chapter cites water-insoluble amphiphiles that have special properties and are able to form insoluble films at the air-water interface. It analyses substances that may form monolayers that consist of molecules that are amphiphilic.

Chapter

Cover Molecular Diagnostics

Recent Technical Advances in Molecular Analysis  

Nadège Presneau and Mary Alikian

This chapter explores the recent technical advances in molecular analysis. It discusses the science and development behind liquid biopsy and digital PCR. The chapter defines liquid biopsy as a minimally invasive procedure used for screening, diagnosis, prognosis, and predictive testing of circulating biomarkers. It regards liquid biopsy as the future of precision medicine. Digital PCR is identified as a highly precise analytical technique for nucleic acids' absolute quantification based on PCR amplification of a single template molecule without the need for a calibration curve. The chapter also includes a range of clinical applications using digital PCR and liquid biopsy.

Chapter

Cover Organometallic Reagents in Synthesis

Metallated alkenes  

This chapter talks about direct and indirect methods that can be used for the preparation of metalated alkenes, including the alkenyl potassium reagent produced using the base potassium amide in liquid ammonia. It examines the equation that shows that allylic deprotonation is a competing reaction that becomes more important as the ring size increases. It also points out how sodium and potassium alkenes are not used in synthesis to anything like the same extent as the corresponding lithium compounds. The chapter describes reactions that are referred to as the lithium-halogen exchange, which is considered as a nucleophilic attack on the halogen atom that occurs with retention of the olefin configuration. The chapter explains that the alternative reaction is the conversion of tin compounds to lithium counterparts wherein the retention of the olefin configuration is observed.