Thermometric titrimetry is particularly suited to the determination of a range of analytes where a precipitate is formed by reaction with the titrant. In some cases, an alternative to traditional potentiometric titration practice can be offered. In other cases, reaction chemistries may be employed for which there is no satisfactory equivalent in potentiometric titrimetry.
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As a result, precipitation titrations often have to be done as back titrations. ;Isothermal titration calorimeter: An isothermal titration calorimeter uses the heat produced or consumed by the reaction to determine the equivalence point. This is important in biochemical titrations, such as the determination of how substrates bind to enzymes. ;Thermometric titrimetry: Thermometric titrimetry is an extraordinarily versatile technique.
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Potentiometric titrimetry has been the predominant automated titrimetric technique since the 1970s, so it is worthwhile considering the basic differences between it and thermometric titrimetry. Potentiometrically-sensed titrations rely on a free energy change in the reaction system. Measurement of a free energy dependent term is necessary. : ΔG0 = -RT lnK (1) Where: : ΔG0 = change on free energy : R = universal gas constant : T = temperature in kelvins (K) or degrees Rankine (°R) : K = equilibrium constant at temperature T : ln is the natural logarithm function In order for a reaction to be amenable to potentiometric titrimetry, the free energy change must be sufficient for an appropriate sensor to respond with a significant inflection (or "kink") in the titration curve where sensor response is plotted against the amount of titrant delivered.
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Collins, A.H., A cell design for radio-frequency titrimetry, accessed 2014-06-29 It evolved into a group of British engineering companies, based in south London, that designed test equipment and provided calibration services.
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Titrimetry is another method of measuring atmospheric carbon dioxide that was first used by a Scandinavian group at 15 different ground stations. They began passing a 100.0 mL air sample through a solution of barium hydroxide containing cresolphthalein indicator.
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This is differentiated from calorimetric titrimetry by the fact that the heat of the reaction (as indicated by temperature rise or fall) is not used to determine the amount of analyte in the sample solution. Instead, the equivalence point is determined by the rate of temperature change. Because thermometric titrimetry is a relative technique, it is not necessary to conduct the titration under isothermal conditions, and titrations can be conducted in plastic or even glass vessels, although these vessels are generally enclosed to prevent stray draughts from causing "noise" and disturbing the endpoint. Because thermometric titrations can be conducted under ambient conditions, they are especially well-suited to routine process and quality control in industry.
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Automated potentiometric titration systems have pre-dominated in this area since the 1970s. With the advent of cheap computers able to handle the powerful thermometric titration software, development has now reached the stage where easy to use automated thermometric titration systems can in many cases offer a superior alternative to potentiometric titrimetry.
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The determination of trace acids in organic matrices is a common analytical task assigned to titrimetry. Examples are Total Acid Number (TAN) in mineral and lubricating oils and Free Fatty Acids (FFA) in edible fats and oils. Automated potentiometric titration procedures have been granted standard method status, for example by ASTM for TAN and AOAC for FFA. The methodology is similar in both instances.
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For example, in the presence of concentrated hydrochloric acid at 100 °C, diphenylphosphine adds to the carbon atom in benzaldehyde to give (phenyl-(phenylmethyl)phosphoryl)benzene. :Ph2PH + PhCHO → Ph2P(O)CH2Ph Compared to tertiary phosphines, diphenylphosphine is weakly basic. The pKa of the protonated derivative is 0.03:C. A. Streuli, "Determination of Basicity of Substituted Phosphines by Nonaqueous Titrimetry", Analytical Chemistry 1960, volume 32, pages 985-987.
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Kolthoff worked in several diverse areas of chemistry. They included acid-base titrimetry, electrometric analysis and conductometry, potentiometry, electron transfer, gravimetric analysis and precipitation reactions, polarographic analysis (voltammetry), amperometric titrations, and emulsion polymerization, among others. His reputation for combining fundamental theory and practical application in his work were characteristic throughout his career. Kolthoff's scientific approach to analysis is widely accepted today, but was rare in the early 1900s when his career began.
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Non-aqueous acid-base titrations can be carried out advantageously by thermometric means. Acid leach solutions from some copper mines can contain large quantities of Fe(III) as well as Cu(II). The “free acid” (sulfuric acid) content of these leach solutions is a critical process parameter. While thermometric titrimetry can determine the free acid content with modest amounts of Fe(III), in some solutions the Fe(III) content is so high as to cause serious interference.
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Borax is also easily converted to boric acid and other borates, which have many applications. Its reaction with hydrochloric acid to form boric acid is: : NaBO·10HO + 2 HCl → 4 B(OH) + 2 NaCl + 5HO The "decahydrate" is sufficiently stable to find use as a primary standard for acid base titrimetry. p. 316. When borax is added to a flame, it produces a yellow green color. Borax is not used for this purpose in fireworks due to the overwhelming yellow color of sodium.
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A burette and Erlenmeyer flask (conical flask) being used for an acid–base titration. Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the titrant or titrator, is prepared as a standard solution of known concentration and volume. The titrant reacts with a solution of analyte (which may also be termed the titrand) to determine the analyte's concentration.
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Thermometric titrimetry offers a rapid, highly precise method for the determination of aluminium in solution. A solution of aluminium is conditioned with acetate buffer and an excess of sodium and potassium ions. Titration with sodium or potassium fluoride yields the exothermic precipitation of an insoluble alumino-fluoride salt. : Al3+ \+ Na+ \+ 2K+ \+ 6F− ↔ K2NaAlF6↓ Because 6 mole of fluoride react with one mole of aluminium, the titration is particularly precise, and a coefficient of variance (CV) of 0.03 has been achieved in the analysis of alum.
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In 1945, Klein attended Brooklyn Technical High School where he took many chemistry courses including inorganic, qualitative and quantitative analysis, organic chemistry, physical chemistry and chemical engineering. After high school, Klein attended Polytechnic Institute of Brooklyn (now New York University Tandon School of Engineering). After briefly debating between Metallurgy and inorganic chemistry, Klein decided to major in inorganic chemistry. Eager to combine his passions of chemistry and electronics, Klein decided to research radio frequency titrimetry for his undergraduate thesis, a new field at the time.
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The technique can be applied to essentially any chemical reaction in a fluid where there is an enthalpy change, although reaction kinetics can play a role in determining the sharpness of the endpoint. Thermometric titrimetry has been successfully applied to acid-base, redox, EDTA, and precipitation titrations. Examples of successful precipitation titrations are sulfate by titration with barium ions, phosphate by titration with magnesium in ammoniacal solution, chloride by titration with silver nitrate, nickel by titration with dimethylglyoxime and fluoride by titration with aluminium (as K2NaAlF6) Because the temperature probe does not need to be electrically connected to the solution (as in potentiometric titrations), non-aqueous titrations can be carried out as easily as aqueous titrations. Solutions which are highly colored or turbid can be analyzed by thermometric without further sample treatment.
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