Ab initio calculation - a method of calculating chemical properties of molecules directly from the first principles of quantum mechanics, without using empirical parameters ie quantities derived from experiments (ab initio is Latin for "from the beginning"). Quantum mechanics is a system of mechanics developed from quantum theory which deals with the behavior of fundamental particles and is used to explain the properties of atoms and molecules.

Activity coefficient - measures the activity of ions with each other in an electrolyte (ion-containing) solution. Ions can complex with each other and also with water.

Adsorption - the accumulation or concentration of a substance on a surface. There are two types; physical adsorption where molecules are attracted and become physically attached to a surface by intermolecular forces of attraction and chemical adsorption in which molecules, atoms or ions are attached to a surface by chemical bonds. Flocculant adsorption to mineral particles is a combination of both types.

Agglomeration - a process occurring in a fine suspension or slurry by which the crystals or solids collide and stick together into larger clumps.

Amperometry - an electrochemical method of analysis in which the current flowing through the working or measuring electrode (where the reaction takes place) of an electrochemical cell is measured.

Anion exchange resin - a resin of synthetic cross-linked polymers which have negatively charged ions (anions) attached to their side-groups. In the anion exchange, different anions in the solution displace these attached anions from the resin. Such resins are used to adsorb desirable anion species from solution.

Anode - the positive electrode in an electrochemical cell at which oxidation occurs, eg where oxygen is evolved when water is electrolysed.

Arsenopyrite - FeAsS, an iron sulfide mineral containing arsenic.

Atomic absorption spectroscopy (AAS) - an analytical technique which uses the absorption of light to measure the concentration of gas-phase atoms. Since samples are usually liquids or solids, the sample must be vaporized. Used particularly to determine metals.

Atomic force microscopy (AFM) - a method of imaging surfaces with atomic or near-atomic resolution. An atomic force microscope uses a very fine tip which acts like the needle of a record player to track across the surface contours of a sample, generating a 3D topographic "map" of its surface features.

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy - ATR is utilised for surface analysis as an accessory for use with FTIR. It uses the same basic principles as FTIR but the infrared light is sent through a crystal which then hits the surface of the sample sitting on top of the crystal to measure the functional groups.

Auger electron spectroscopy (AES) - a form of electron spectroscopy which identifies the elemental composition (excluding hydrogen and helium) of the top few layers of a surface by measuring the energies of the Auger electrons ejected from near-surface atoms when a solid sample is bombarded with an electron beam. These energies are characteristic of the elements from which the electrons come. The spatial distribution of an element across the surface can also be determined.

Bayer process - a hydrometallurgical process for extracting alumina (aluminium oxide) from bauxite ore, which produces the majority of the world's alumina. It has four stage - digestion, clarification (solid-liquid separation), gibbsite precipitation and calcination.

Calcination - the final stage in the Bayer process in which washed and dried gibbsite (alumina hydrate) is heated at high temperatures to drive off the water of crystallisation (dehydration) and obtain alumina, a fine white powder.

Calorimetry - measurement of the heats of chemical reactions.

Cathode - the negative electrode in an electrochemical cell at which reduction occurs, eg where copper is plated from an acidic copper sulfate solution.

Cation - a positively charged ion.

Chalcocite - Cu₂S, an ore of copper.

Chalcopyrite - CuFeS₂, a widely distributed yellow mineral consisting of a sulfide of copper and iron in tetragonal crystalline form. This copper ore is a major source of copper

Chemical speciation - the chemical species (ions and molecules) present in a solution.

Colloidal gold - fine particles of gold suspended in a solution which looks red. Colloidal gold reacts with cyanide to form a colourless gold cyanide complex. The rate at which the solution loses colour is determined by the free cyanide concentration ie the cyanide actually available to leach the gold.

Column chromatography - a method for analysing or separating the components or dissolved substances of liquid mixtures. The sample is poured into the top of a column packed with an adsorbing material and washed through with a solvent. Different components adsorb to different extents and so move through the column at different rates. They are eluted in the liquid from the bottom of the column at different times as fractions. If the column material is more polar than the solvent, the components are separated by their differences in polarity, with the less polar components passing through the column faster than more polar ones.

Comminution - particle size reduction by breaking, crushing or grinding of ore to reduce ore to the size required for mechanical or chemical separation.

Computational fluid dynamics (CFD) - computer modelling of the flow behavior or the patterns of flow in a fluid, used for example to describe the complex flow of liquid and solids during flocculation in a thickener and during crystallisation in a stirred precipitator.

Copolymers - chemicals having large molecules consisting of chains of different lengths of two repeated units or monomers, in which there can be different arrangements of the monomers A and B.

Crystal dislocation - a type of crystal defect, which is a line defect in a crystal lattice that may run the length of the crystal. There are different kinds of line defects, such as those due to a missing row of atoms. Dislocations are formed when a crystal is grown.

Crystal twinning - a type of crystal defect in which two or more crystals of the same material intergrown so that they have one or more planes, but not all, in common.

Cyclic voltammetry - a transient method for investigating electrochemical reactions in which the voltage is cycled between limits and the current followed with voltage and time. The current as a function of voltage is plotted as a cyclic voltagramm.

Desilication product (DSP) - a discarded by-product (aluminosilicate) formed by desilication, a specific alumina refinery operation for the removal of silica from the Bayer liquor by precipitation (in the digestion vessels).

Dielectric relaxation spectroscopy (DRS) - probes the interaction of a sample with a time-dependent electric field. The resulting polarisation (separation of charge) characterises the charge-density fluctuations within the sample. DRS is specific for chemical species with a permanent dipole moment (involves a pair of separated opposite electric charges), like an ion-pair of a positively charged ion and a negatively charged ion.

Diffuse reflectance-Fourier transform infra red spectroscopy - diffuse reflectance is an accessory used with FTIR for surface analysis, in which the diffusely reflected light (that which is scattered within a sample and returned to the surface) resulting when an infrared beam reflects off a rough surface is detected to produce the infrared spectrum.

Digestion - the first stage in the Bayer process in which crushed bauxite is mixed with a concentrated caustic soda (sodium hydroxide) solution and heated under pressure to dissolve the alumina.

Eh - the electric potential or voltage of an electrode (the potential difference between the electrode and the solution) relative to the hydrogen reference electrode (also known as the standard hydrogen electrode), also called the solution potential or the standard electrode potential.

Electrochemistry - the study of charge separation and charge flow and their relationship to chemical systems. It is the science of the interaction of phases containing electrons and phases containing ions ie the science of electron transfer across a solution-electrode interface. Electrochemistry happens at surfaces. Electrochemical reactions are chemical reactions in which electrons are transferred.

Electrochemical cell - a system in which two electron conductors (the electrodes) are in contact with a conducting solution of ions (the electrolyte). The ionic and electronic conductors are connected so as to form a complete circuit through which charge can move. The charge is carried by electrons in part of the circuit and by ions in the electrolyte. Oxidation occurs at one electrode (the anode) while reduction takes place at the other (the cathode). So the electrons flow from the anode to the cathode.

Electrochemical impedance spectroscopy - a powerful tool for examining many chemical and physical processes in solutions as well as solids. It applies impedance spectroscopy to electrochemical systems. The impedance is the ratio of the applied voltage to the current passed when a variable voltage (ac) is applied to a material. In many materials, the impedance varies as the frequency of the applied voltage changes, due to the properties of the liquid or solid. This technique plots measurements of impedance over a suitable frequency range on suitable axes and relates the results to the physical and chemical properties of the material.

Electrowinning - a technique used in mineral processing to recover a metal (such as copper, zinc or nickel) from a solution containing the metal ions. An electrowinning production cell is an electrochemical cell with an applied electric current in which metal ions deposit or plate as the metal on the cathode.

Energy dispersive spectroscopy (EDS) - a technique for element identification based on the characteristic X-ray peaks generated when the high energy electron beam of an electron microscope interacts with a sample surface. The X-rays emitted by the excited atoms are characteristic of the elements present and can also be used to determine the relative concentrations of each element.

Extended X-ray absorption fine structure (EXAFS) - a type of X-ray absorption spectroscopy used to obtain structural information about molecules. Analysis of the X-ray absorption spectrum of the absorbing element provides information about the local structure around the studied atoms such as distance, type and number of the surrounding atoms. For example, aluminium EXAFS analysis gives information about the nearest neighbouring atoms surrounding aluminium atoms.

Feedwell - the entry feedwell of a thickener tank is where the flocculant is added to, and mixed with, the feed (the solid-liquid suspension) entering the thickener, before the flocculated suspension exits into the settling area of the thickener.

Flash train - in an alumina refinery, the hot slurry produced by digestion is passed through a series of flash tanks (the flash train), allowing stepwise flashing or boiling of the slurry which progressively reduces the pressure of the digested slurry and cools it to atmospheric boiling temperature.

Flocculants - are polymers (chemicals having large molecules consisting of chains of different lengths of repeated units or monomers), used in the Bayer process to flocculate bauxite residue and sometimes also the alumina hydrate product. Flocculants aggregate fine particles by bridging or sticking the particles together to form larger clumps or aggregates.

Flocculation - the process by which fine particles in a solid-liquid suspension aggregate into larger clumps, which speeds up solid-liquid separation.

Flow field-flow fractionation (FlowFFF) - a technique that separates the polymer molecules making up a flocculant by size.

Focused beam reflectance measurement (FBRM) probe - an instrument used by the Parker Centre for the sizing of aggregates from flocculated mineral suspensions. It can determine the aggregate size distributions achieved under different flocculation conditions. It tracks the rate and degree of change to both aggregate dimension and aggregate number, allowing in situ monitoring of flocculation performance in the lab and in industrial thickeners.

Fourier transform infrared (FTIR) spectroscopy - an analytical technique used to characterise and identify organic (and in some cases inorganic) materials by detecting infrared absorption by the sample pellet. The infrared spectrum of an organic compound provides specific information about chemical bonding and molecular structure eg the functional groups that are present.

Gangue - the unwanted or worthless rock and other waste materials present in an ore deposit.

Gas chromatography-mass spectrometry (GC-MS) - a powerful tool for organic analysis. It separates the various components in a mixture of volatile chemical compounds by GC. Then a mass spectrum (mass-to-charge ratio) is generated for each component as it elutes from the GC column. Each compound is identified from its unique mass spectrum.

Gibbsite - gibbsite (aluminium hydroxide, also called alumina hydrate - Al₂O₃.3H₂O) is an intermediate in the Bayer process for extracting alumina from ore.

Heat capacity - the ratio of the heat supplied to a substance to its consequent rise in temperature.

Hematite - a mineral form of iron(III) oxide (Fe₂O₃) and an important ore of iron. It is a major component of bauxite residue, the waste material from the digestion stage of the Bayer process.

High performance liquid chromatography (HPLC) - a sensitive technique for separating and analysing mixtures. It is a form of liquid chromatography in which the sample is forced through the chromatography column under pressure by high-pressure pumps. HPLC is useful for separating compounds that are dissolved in solution and results in an excellent separation in a relatively short time.

Hydrocyclone - industrial equipment which uses the principle of centrifugal separation to remove or classify solid particles from a fluid, based on size, shape and density.

Hydrodynamics - the study of the motion of fluids, the study of how physical forces (pushes and pulls) affect fluids, especially liquids. Mixing and other flow related processes such as shear rate and flow patterns are collectively called hydrodynamics.

Hydrometallurgy - the extraction (the chemical processing of a mineral to yield a desired product) of metals and metallic compounds such as gold, alumina, nickel, copper and zinc from minerals by solutions. The alternative method of processing mined ores is pyrometallurgy using high temperature (>1000^oC) extractions.

Interfacial tension - at the liquid-liquid interface between two dissimilar liquids (eg aqueous and organic phases), there will be interactions between molecules of different type. The interfacial tension between the two phases arises due to the attractive forces between the molecules in the different fluids.

Ion-association - ion-ion interactions between ions in an electrolyte (ion-containing) solution.

Ion-pair - involves a charge attraction between a positively charged ion and a negatively charged ion which act as a pair rather than behaving as independent ions. Ion-pairs result from ion-ion interactions in electrolyte solutions. Identification and quantitative determination of ion-pairs is important for understanding electrolyte properties and modelling industrial processes.

Ionic strength - expresses the effect of the charge of the ions in a solution. It is determined by the concentration and charge of each of the different ions present in a solution.

Kaolin - a major component of many mineral tailings. It is found in bauxite and ends up as DSP (desilication product) in the bauxite residue of the Bayer process. Kaolin is composed mainly of the mineral kaolinite (Al₄Si₄O₁₀(OH)₈).

Kinetics - the branch of chemistry concerned with measuring and studying the rates of chemical reactions. The main aim is to determine the mechanism of reactions by studying the rate under different conditions eg temperature, pressure, concentration.

Laminar flow - the flow of a fluid when the fluid flows smoothly without turbulence. Laminar flow is much simpler than turbulent flow and the shear gradients are more clearly defined and uniform.

Laser Doppler velocimetry - a method for measuring the speed of small particles suspended in a flowing fluid. It is non-invasive since laser light is the measuring tool and can be used to study particle behavior. The Doppler shift (also used in police radar) of the light scattered by particles provides information about the velocity of the particles.

Laterite - a red residual soil developed in humid, tropical, and subtropical regions. It contains iron oxides and hydroxides and aluminum hydroxides. Nickel laterite is rich in nickel.

Leaching - a process used in mineral processing to recover metals from ores by dissolving the metal into a solution in contact with the crushed ore. There are different types of leaching, including high temperature acid or alkali leaching, cyanide leaching of gold and bacterial or bioleaching of sulfide minerals.

Linear sweep voltammetry - a general term applied to any voltammetric method for studying electrochemical reactions in which the potential applied to the working electrode is varied linearly in time. Voltammetry refers to the measurement of current that results from the application of potential.

Lithotrophic microbes - rock-eating microorganisms which live on a mineral diet by oxidising inorganic compounds (such as sulfide, ammonia and nitrite) to obtain food and energy.

Low energy electron diffraction (LEED) - a powerful technique for studying the structure (the arrangement of atoms) of crystalline surfaces and processes occurring on these surfaces and the resulting changes. The sample is bombarded with a beam of low energy electrons which are diffracted or scattered by the surface atoms. The diffraction pattern or 3D geometric distribution of the scattered electrons is determined by the structure of the surface.

Mixed potential - the electric potential or voltage of a reacting electrochemical system with two different redox couples. For example, in the dissolution of copper by ferric ions in strong chloride solutions, the mixed potential is the potential for the reaction:
Fe³⁺ + Cu ® Fe²⁺ + Cu⁺.

Molecular modelling - utilises computer simulations to model chemical structures or processes (such as crystal growth) at a molecular level. It makes use of theoretical chemistry and complex mathematical equations. It is a technique for deriving, representing and manipulating the structures and reactions of molecules, and those properties that are dependent on these three dimensional structures. It involves doing chemistry on computers with virtual molecules.

Multi-angle laser light scattering (MALLS) - a technique that uses the amount that the flocculant molecules in each narrow FlowFFF-separated size fraction scatter its laser light to measure the average molecular weight of each fraction. Used together, the two techniques produce molecular weight distributions of flocculants, rather than the average possible with MALLS alone, and without destroying the sample.

Nuclear magnetic resonance (NMR) - NMR spectroscopy is useful for chemical analysis and determining the structure of molecules because the resonance frequency of a particular element are influenced by the atom's chemical surroundings. It can determine the chemical structure of organic compounds.

Nucleation - the precipitation process involving the "birth of a new crystal" ie the initial formation of a crystal. Primary nucleation is nucleation in an unseeded system. Secondary nucleation is the process in which, as the crystals in a stirred precipitator rub past or bash into each other or the walls, fine chip-like particles are generated. These are used as seed crystals.

Neutron diffraction - a technique analogous to X-ray diffraction that uses the scattering of neutrons by atoms in solids, liquids or gases to determine atomic arrangements. It is much more effective than X-ray diffraction in locating low-atomic-number atoms (light elements) such as hydrogen because the diffraction patterns are produced by interaction of the neutrons with atomic nuclei rather than by interaction with the extranuclear electrons as in X-ray diffraction.

Overflow - the clarified or separated liquid output from the solid-liquid suspension added to a thickener, which should have only a minimal solids content.

Oxidation - loss of electrons by atoms or ions in a chemical reaction.

Particle vision and measurement (PVM) - the PVM probe at CSIRO Minerals has been used in studies of the flocculation behaviour of both model and plant mineral suspensions. It can capture images in situ with a resolution of 5 µm, and allows the shape and structure of aggregates to be evaluated without sampling or dilution. It complements focused beam reflectance measurement (FBRM) instruments, allowing both in situ sizing and imaging under a wide range of conditions.

Passivation - the formation of a thin passive film or layer on the surface of a metal or mineral that acts as a protective coat to protect the underlying surface from further chemical reaction. In current-voltage plots of passivation, the current, instead of increasing with voltage, falls to a very small value.

Physico-chemical properties - Physical properties (eg density, viscosity and heat capacity) that are affected by chemical structure. Physical chemistry is the study of the physical changes associated with chemical reactions and the dependence of physical properties on chemical composition - it includes electrochemistry.

Pipe reactor - a linear pipe system used by CSIRO Minerals for investigating the rates under different conditions of the flocculation "reaction" that controls the formation and rupture of aggregates. Flocculant is introduced into a pipe through which the feed suspension flows and the focused beam reflectance measurement (FBRM) probe is used to measure the change in aggregate size as a function of reaction time.

Population balance model - a mathematical model for predicting the change in particle/aggregate/agglomerate size distribution through time (ie it tracks the number and size of these species as they form or rupture). It requires mathematical relationships to be developed that describe each growth or rupture process, with the balance usually written as a series of inter-related equations.

Potential - the electric potential or voltage of an electrochemical system. For electrochemical cells that contain an anode and a cathode, the potential difference between the cathode electrode potential and the anode electrode potential is the potential of the electrochemical cell.

Potentiometry - involves the measurement of potential for quantitative electrochemical analysis.

Potentiostat - an electronic instrument that controls the electrical potential between the working and reference electrodes of a three-electrode (working, counter and reference electrodes) electrochemical cell at a preset value. It forces the necessary current to flow between the working and counter electrodes to maintain the desired potential, within the limits of the potentiostat.

Precipitation - the chemical process in which a dissolved substance separates from solution as a fine suspension of solid particles. Also called crystallisation when the solids formed are crystals.

Precipitator - a tank or vessel in which the solid product is precipitated as crystals from a stirred supersaturated solution.

Preg-robbing - is the term used to describe the adsorption of cyanide-leached gold by ore components which are usually carbonaceous (contain carbon) in nature. This robbing of gold from the pregnant liquor or the solution of gold-cyanide obtained by cyanide leaching of finely ground gold ore makes gold extraction from such ores less profitable. The preg-robbing index of an ore is a number that indicates the extent or degree of preg-robbing.

Prismatic faces - the faces (the flat surfaces of a crystal) in a crystal which are parallel to the vertical axis.

Pyrite - a mineral form of iron sulfide, FeS₂.

Pyrrhotite - FeS, an iron sulfide mineral.

Rake - a thickener has a large powerful rake at its base to move the settled solids to the discharge point and out in the underflow.

Raman spectroscopy - a light scattering technique used to determine molecular structure and for non-destructive chemical analysis. It is based on the Raman effect which arises when incident light excites molecules in a sample which subsequently scatter the light. While most of this scattered light is at the same wavelength as the incident light, some is scattered at different wavelengths. The new wavelengths in the Raman spectrum are characteristic of the substance.

Redox - reduction-oxidation, a chemical process involving the transfer of electrons from one atom, ion or molecule to another, in which one reaction is an oxidation (loss of electrons) and the reverse reaction is a reduction (gain of electrons).

Refractory sulfide ores - the primary sulfide gold ores often found in underground deposits in which the gold is "locked" away from the leaching cyanide within the sulfide mineral matrix as extremely small grains or at the atomic level in the matrix structure. Gold present in such a matrix is liberated by an oxidative step (eg by roasting, by bacteria or by pressure oxidation) prior to cyanide leaching.

Resin-in-pulp - a modern method for the separation and purification of metal ions from leach solutions using ion-exchange resins (specific solid adsorbents). This technique offers the potential for the direct recovery of metal ions from pulps as practised in the carbon-in-pulp process for the recovery of gold. An in-pulp recovery process avoids having to do solid-liquid separation before recovery.

Rest potential - the potential to which an electrochemical system will naturally approach if no external voltage is applied.

Rheology - the study of the flow and change of shape of matter (flow properties), especially the viscosity of liquids. An understanding of the rheology of mineral suspensions is important in many hydrometallurgical operations, such as pumping, pipeline transport, thickening, milling and grinding.

Rietveld analysis - a mathematical way of working out the concentrations of the components of a material from its X-ray diffraction pattern.

Rotating disc electrode (RDE) - a specialised hydrodynamic electrode used in electrochemical studies for ensuring a known and controllable flow of solution over the electrode. The flat disc electrode is rotated in the solution.

Rotating ring-disc electrode (RRDE) - a specialised variant of the rotating disc electrode which includes a second electrode - a concentric ring electrode - that is placed outside the disc and used to analyse species generated on the disc. The ring is electrically insulated from the disc so that their potentials can be controlled independently.

Scale - a mineral deposit or encrustation produced when dissolved minerals precipitate out of solution. Scale is to industrial heat exchange surfaces, equipment surfaces, membranes and plant pipes and reactors what barnacles are to ships.

Scanning auger microscopy (SAM) - a type of electron microscopy for compositional mapping of a surface by irradiating a sample surface with a focused high energy electron beam and then detecting the emission of electrons known as Auger electrons. The energies of these Auger electrons are characteristic of the element from which they are generated. It provides information on what elements are present on the surface, their concentration and chemical state and maps their spatial distribution.

Scanning electron microscopy (SEM) - produces high resolution images of the morphology or topography of the sample surface by imaging the electrons reflected when the sample is scanned with an electron beam. Monitoring the secondary X-rays produced by the electron-sample interaction using energy dispersive spectroscopy for element identification allows compositional analysis.

Scanning tunnelling microscopy (STM) - a method used to investigate surfaces of electrically conducting materials to determine the surface structure (atom type and arrangement). A fine metal tip is scanned across a sample (very close to the surface) in order to construct an image of the surface by sensing corrugations in the electron density of the surface that arise from the positions of surface atoms. The contours of the features of the atomic surface are mapped out. The corrugations are sensed by detecting the electrons which "tunnel" through the gap, the region of vacuum, between the tip and the sample.

Scanning tunnelling spectroscopy - provides a 3D map of the local electronic structure of a sample's surface. The electronic structure of an atom depends upon what element it is and also upon its local chemical environment, such as how many neighbors it has, what kind of atoms they are and the symmetry of their distribution.

Secondary nucleation - the precipitation process in which, as the crystals in a stirred precipitator rub past or bash into each other or the walls, fine chip-like particles are generated. These are used as seed crystals.

Seed crystals - are small crystals added to a supersaturated solution being agitated in a precipitator to induce crystallisation and grow a crop of large crystals for harvesting.

Shear rate - the rate at which a fluid is sheared. Shear is the stress or deforming force that occurs as parallel planes slide over one another. It is a flow related process and affects the size and quality of the gibbsite crystals produced in precipitators.

Shear vessel - a laboratory mixing vessel in which there are reproducible mixing conditions for mixing flocculant and a solid-liquid suspension, developed by CSIRO Minerals for flocculation studies.

Slurry - a solid-liquid suspension, such as that produced when a caustic soda (sodium hydroxide) solution is mixed with finely ground bauxite ore.

Solution potential - see Eh above.

Solvent extraction (SX) - a process used to selectively separate dissolved metals such as uranium, copper, nickel, cobalt and vanadium from impurities or each other. A solution of a metal leached from an ore is mixed with an organic solvent containing specialist extractant chemicals. The aqueous and organic phases form an emulsion in which the extractant chemicals in the organic solvent bind to the metal ions and pull the metal into the organic phase. The mixture is left to settle so that the organic and aqueous phases separate. The organic phase containing the concentrated, purified metal is removed. The metal ions are then transferred from the solvent back into an aqueous solution from which they can be recovered in high purity.

Sterically hindered - the prevention or retardation of inter- or intramolecular interactions as a result of the spatial structure of a molecule (the arrangement of atoms and groups) which blocks interactions.

Supersaturation - in a saturated solution, the dissolved substance (solute) is in equilibrium with undissolved substance ie the rate at which solute particles leave the solution to return to their solid state is equivalent to the rate at which they dissolve into solution. A solution containing more than the equilibrium amount of the dissolved substance at a given temperature is supersaturated. A supersaturated solution is not stable and if a small seed crystal of the substance is added, the excess solute will crystallise out.

Surfactants - are surface-active compounds which tend to gather on the surface between two chemical phases, such as a water-air interface or a solid-liquid interface. Froth-producing household washing detergents are surfactants.

Taylor-Couette precipitator (TCP) - a novel laboratory precipitator which can be run at constant or well defined shear rates. Used to study the effects of hydrodynamics (shear rate and mixing) on the precipitation processes of crystal nucleation, growth and agglomeration, and in turn, on the crystal yield and quality.

Thermal analysis - techniques for the identification and the investigation of the products formed by heating a substance. Examples include thermogravimetry-Fourier transform infrared (TG-FTIR) spectroscopy and thermogravimetry-mass spectrometry (TG-MS). Thermogravimetry is a technique that quantifies mass changes during controlled heating of a solid. The spectrometers enable identification of evolved gases as a function of temperature.

Thermodynamics - study of the relationship between heat, work, temperature and energy, useful in predicting the behavior of systems at equilibrium.

Thickeners - are large shallow tanks used to separate solids from liquids in a range of mineral processing industries such as alumina, gold, diamonds and mineral sands. The solids in the solid-liquid suspensions put into thickeners are usually fine particles which sink very slowly to the bottom. To speed up the separation process, flocculants are mixed into the suspensions. These stick the fine particles together to form larger clumps or aggregates that settle out faster. A flocculant is mixed with a suspension in the entry feedwell of a thickener.

Titration calorimetry - is a technique that measures the heat of interaction when substances interact and generate or adsorb heat, as the relative amounts of the substances are varied. This is done by mixing the substances inside a sensitive calorimeter, using titration to precisely control the amount of each substance put into the system.

Tomography - techniques used to obtain an image of a selected plane section within an object. It creates cross-sectional images or slices in 3D of the interior of the investigated object without physically cutting it. Conductance tomography for determining 3D solids distributions within thickener feedwells and the bulk of thickeners involves measurement of changes in conductivity between a number of sensors.

Transmission electron microscopy (TEM) - a type of microscopy in which an electron beam transmits through or passes through a specimen onto a fluorescent screen where a visual magnified image is formed. TEM is used to determine the internal microstructure of materials.

Turbulent flow - the flow of a fluid that flows turbulently with vortices or other turbulence in which the motion at any point varies rapidly in direction and magnitude and fluid particles move in series of eddies or whirls.

Ultra high vacuum (UHV) - a space where there is a very low pressure of gas ie relatively few atoms or molecules. UHV is required for most surface science studies. It enables atomically clean surfaces to be prepared for study, which would otherwise be contaminated immediately in air. It also allows clean surfaces to be maintained free of contamination while the surface is being imaged or analysed.

Underflow - the discharge from the bottom of a thickener, which should have a high concentration of settled waste solids from the solid-liquid suspension added to a thickener.

Voltammetry - electrochemical measuring techniques which measure the current that results from the application of potential to drive an electrochemical reaction.

Water activity - indicates how tightly water is bound to other molecules in a sample. It is a direct measurement of the free, unbound or "active" water that is available to participate in chemical reactions.

Xanthate - any salt or ester of xanthic acids, organic sulphur-containing acids. Xanthates can adsorb to the activated carbon used to adsorb gold cyanide complexes from solution in gold processing, which fouls the carbon. Xanthates are widely used to concentrate minerals by froth flotation.

X-ray diffraction (XRD) - is used to determine the structure of crystals. When X-rays are beamed at a crystal, electrons diffract the X-rays, which produces a diffraction pattern. Since X-ray scattering depends upon electron density, the diffraction pattern can be converted into an electron density map. Since electrons more or less surround atoms uniformly, it is possible to fit a molecular structure to this map and determine where atoms are located in the crystal and what atoms are there.

X-ray photoelectron spectroscopy (XPS) - provides information on what elements are present in the surface layers of a sample, their relative quantities and how they are chemically combined. X-ray excitation can eject electrons from a solid - if an X-ray photon or particle with a high enough energy strikes an atom, an electron (a photoelectron) can be removed from the atom. The energy with which each expelled electron was bound to its atom can be determined by analysing these photoelectrons. An electron's binding energy acts like an ID for the specific element it came from - and varies slightly according to the chemical environment of its atom. XPS can also produce images or maps that show the physical distribution of particular chemical species over the sample's surface.