Applications of a new low temperature differential scanning calorimeter

A new low temperature differential scanning calorimeter is described which operates over the temperature range –150 °C to 700 °C. The equipment features a chromel heat flux DSC sensor plate located in a cobalt alloy heating chamber, enabling work to be carried out in oxidizing atmospheres to above 600 °C. Full data processing and programme control facilities are provided by an IBM compatible computer system. The performance of the instrument is illustrated by experiments on indium and poly (vinyl chloride).

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Zusammenfassung Ein neues Tieftemperatur-Differential-Scanning-Kalorimeter für den Bereich von –120 °C bis+700 °C wird beschrieben. Das Gerät enthält eine Wärmefluss-DSC-Sensorplatte aus Chromel in einer Heizkammer aus einer Kobaltlegierung, was Arbeiten in oxidierender Atmosphäre bis über 600 °C ermöglicht. Ein IBM-kompatibles Computersystem bietet alle Möglichkeiten der Datenverarbeitung und Programmregelung. Die Leistungsfähigkeit des Geräts wird an Hand von Experimenten mit Indium und Polyvinylchlorid demonstriert.

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, —150° 700°. , 600°. IBM . .

     

Acid hydrolysis of cellulose in a differential scanning calorimeter

Differential scanning calorimetry was applied to the decompositions of cellulose and D-glucose with several concentration of sulfuric acid. The heat of reaction for cellulose was slightly less than that for glucose. It suggests that the heat of hydrolysis of the (-1,4-glucosidic linkage is endothermic.The degree of reaction obtained by means of a commercial kinetic program was 1.1±0.1, which was independent of the acid concentration for both cellulose and glucose.The quantity of D-glucose produced by saccharification of cellulose was estimated using kinetic parameters obtained for cellulose and glucose, which were assumed to express the respective parameters for the successive first-order reactions cellulose to D-glucose, and glucose to decomposition products.

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Zusammenfassung Die Zersetzung von Cellulose und D-Glucose durch Schwefelsäure unterschiedlicher Konzentration wurde mittels DSC untersucht. Die Reaktionswärme ist bei Cellulose etwas geringer als bei Glucose, was zeigt, daß die Hydrolyse der-1,4-Glucosidbindung ein endothermer Vorgang ist. Der mittels eines kommerziellen kinetischen Programms erhaltene Reaktionsgrad beträgt 1.1±0.1 und erwies sich sowohl bei Cellulose als auch bei Glucose als unabhängig von der Säurekonzentration. Die durch Verzuckerung von Cellulose gebildete Menge an D-Glucose wurde unter Verwendung von für Cellulose und Glucose erhaltenen kinetischen Parametern bestimmt, für die angenommen wurde, daß sie die entsprechenden Parameter der Folgereaktionen erster Ordnung Cellulose D-Glucose und Glucose Zersetzungsprodukte darstellen.

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-. - , . , - -1,4- . , , 1.1±0.1 . -, , , , - .

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We express our sincere gratitutde to Dr. S. Tanaka for useful discussions.     

Disc — A differential isoperibol scanning calorimeter

The construction and operation of a new fully automated microcalorimeter is described.This instrument allows specific heat measurements to be performed on small samples in the 10 mg-range at low temperatures (10 K <T < 350 K). The new method consists of ombining the non-adiabatic relaxation-time calorimetry with a twin arrangement and simultaneous temperature scanning. Some experimental details of the calorimeter and sample holders are presented. The accuracy of the calorimeter was verified by calibration measurements on 56 mg of copper. An energy resolution of 0.1J/K has been reached near 12 K. To demonstrate the reliability of the microcalorimeter the heat capacity of the new highT _c superconductor YBa₂Cu₃O_7–y, was determined.

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Zusammenfassung Konstruktion und Betrieb eines neuen vollautomatischen Mikrokalorimeters werden beschrieben. Mit dem Instrument können Messungen von spezifischen Wärmen an kleinen Proben im 10-mg-Bereich bei tiefen Temperaturen (10 K <T < 350 K) durchgeführt werden. Mit der neuen Methode werden die nichtadiabatische Relaxationskalorimetrie mit der Zwillingsanordnung und gleichzeitigem Temperaturscanning kombiniert. Das Meßsystem des Kalorimeters mit der Probenhalterung wird genauer vorgestellt. Die Genauigkeit des Kalorimeters wird durch Eichmessungen mit einer Kupferprobe (56 mg) geprüft. Nahe 12 K wurde eine Auflösung von 0.1J K^–1 erzielt. Die Zuverlässigkeit des Mikrokalorimeters wird an einer Bestimmung der spezifischen Wärme des neuen Supraleiters YBa₂Cu₃O_7–y demonstriert.

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. ( 10 ) 10 < < 350 . - . . 56 . 0,1 / 12 . _C YBa₂Cu₃O_7-y .

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The authors like to thank Susanne Lederer for setting up and testing part of the equipment.     

The DSC12E,a low-cost differential scanning calorimeter

The DSC12E is a low-cost Differential Scanning Calorimeter, specially developed for quality control- and educational purposes. A discussion is given of the various boundary conditions connected to the development of this instrument and the resulting construction is described. The specifications of the instrument are discussed with the aid of some illustrative experiments.

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Zusammenfassung Das DSC12E ist ein Differential Scanning Calorimeter der niedrigsten Preisklasse, das sowohl für die QualitÄtskontrolle im Routinelabor als auch für Ausbildungszwecke entwickelt wurde. Es werden die Spezifikationen und die Rahmenbedingungen dieses Instrumentes erlÄutert und erste Messungen dargestellt.

     

Enthalpy of solution of carbohydrates using a modified differential scanning calorimeter

A differential scanning calorimeter (DSC) was modified for the determination of enthalpies of solution. The measurements were performed on aqueous solutions of the deoxy- and fluoro-deoxy derivatives of D-glucopyranose (Glu) where the OH group on the C1, C2, C3, and C6 is replaced by H (1HGlu, 2HGlu, 3HGlu, and 6HGlu) and by F (1FGlu, 2FGlu, 3FGlu, and 6FGlu), 4-deoxy 4-fluoro--D-glucopyranoside (4FGlu), 1-methoxy--D-glucopyranoside (MeOGlu), 1-phenoxy--D-glucopyranoside (PheOGlu), D-mannopyranose (Man), and 3-methoxy--D-glucopyranoside (3MeOGlu), at 15.1, 25.0, 35.0, and 45.1°C. The enthalpies of solution _sH⁰(T) ranged from 1.00±0.25 kJ-mol^–1 for 6HGlu at 15.1°C to 20.4±1.4 for PhOGlu at 45.1°C and were in good agreement with literature values for Man, Glu, MeOGlu, and 3MeOGlu at 25.0 and 35.0°C and for MeOMan and 2HGlu at 35.0°C. _sH⁰(T) for the derivatives were then extrapolated up to the melting temperature T_m and compared with their enthalpies of fusion, _fH also determined from DSC measurements. If the agreement between _sH⁰(T_m) and _fH was within the 95% confidence level, then it was concluded that intermolecular interactions between the carbohydrate molecules in the liquid phase were the same as between the carbohydrate and water molecules in the solution phase. This agreement was observed for aqueous solutions of Man, Glu, MeOGlu, 3HGlu, 3FGlu, and 6FGlu.     

New differential scanning calorimeter. New thermochemical applications

The described calorimeter is of fluxmetric, differential type. Thanks to the surrounding arrangement of the heat-flux-sensor, the sensitivity is independent of the sample characteristics: size, container type, kind of gas etc. Application to high-pressure experiments, is outlined. The general arrangement gives direct access to the sensitive zone from the outside: direct introduction of the sample; setting of electrical, mechanical, or pneumatic connections; application to the study of “open” chemical systems (gas-solid reactions). Examples of application are given.     

Comparative analysis of purity determination methods using a differential scanning calorimeter

Comparative analysis of several methods for purity determination using DSC is presented. This is based on a mathematical model including the construction of theoretical melting curves for two-component systems and the calculation of recorded melting curves with the help of a set of equations describing the formation of a DSC output signal. It is shown that the true accuracy of purity determinations in the range of impurity concentrations ¯x=0.005–0.02 does not exceed 30–50%.

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Zusammenfassung Eine Vergleichende Analyse verschiedener Methoden zur Reinheitsbestimmung mittels DSC wurde ausgeführt. Diese basiert auf einem mathematischen System, daß die Konstruktion theoretischer Schmelzkurven für Zweikomponentensysteme und die Berechnung von registrierten Schmelzkurven mit Hilfe einer Reihe die Ausbildung des DSC-Signals beschreibenden Gleichungen in sich einschließt. Es wird gezeigt, daß die Genauigkeit der Reinheitsbestimmungen bei Konzentrationen der Verunreinigungen von ¯X₂=0.005–0.02 30–50% nicht überschreitet.

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, , . , 0,005-0,02 30–50%.

     

Application of the differential scanning calorimeter to purity measurements

This paper presents a new method for the calculation of the purity of organic, non-polymeric samples using the recorder trace from a Differential Scanning Calorimeter (DSC), Perkin-Elmer Corp. The entire DSC recorder trace is employed rather than only the initial portion of the curve. The previous trial and error choice of energy lost by the DSC trace has been replaced by a definite numerical value. Meaningful purity values have been obtained from a single DSC trace on samples of from 95 to 99.9% purity. This new method has been demonstrated to provide more accurate and less ambiguous results than the manufacturer's procedure.     

Enthalpies and temperatures of transformation for plutonium using a differential scanning calorimeter

The enthalpies and temperatures of transformation of high purity plutonium were measured using a differential scanning calorimeter. The results of our study are presented and compared to values obtained by previous methods.Work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore Laboratory under contract No. W-7405-Eng-48.     

Characterization of solid dispersions of rofecoxib using differential scanning calorimeter

Summary Solid dispersions were prepared to enhance the dissolution rate of rofecoxib. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used for the characterization of solid dispersions of polyvinyl pyrrolidone (PVP):talc:drug (3:1:1) and hydroxypropyl methylcellulose (HPMC):talc:drug (4:1:1). The DSC study indicated that PVP solid dispersion showed formation of fusion solution while HPMC solid dispersion showed no intermolecular fusion during the preparation of solid dispersions by spray dry process. The dissolution profiles and the calculated times for 75 and 90% drug release showed that dissolution rate of rofecoxib was improved in solid dispersions as compared to pure drug and physical mixtures. The DSC and XRD were successfully employed to find out the crystalline state of drug in the both solid dispersions. PVP solid dispersion gave better dissolution rate than HPMC solid dispersion. The drug was transformed from crystalline to amorphous form in PVP solid dispersion which was further conformed by XRD and DSC. The PVP:talc:drug solid dispersion can be used for the dissolution enhancement and thereby bioavailability of rofecoxib.     

Thermal studies on tetrazole derivatives using a differential scanning calorimeter. I

The thermal decomposition of arylidene tetrazolyl hydrazones has been studied under dynamic and isothermal conditions using a differential scanning calorimeter. Attempts have been made to evaluate the thermochemical and kinetic parameters of these compounds. It has been observed that the thermal stability of the tetrazole derivatives decreases with increasing substitution of nitro groups in the aromatic ring.     

A study of sulfur-free thiuram vulcanization using differential scanning calorimeter

A number of curative mixtures without rubber and with natural rubber or polybutadiene based on binary and tertiary combinations of zinc oxide, tetramethylthiuram disulfide, and 2-mercaptobenzothiazole were treated in a differential scanning calorimeter. From the shapes of exothermal curves a zinc-accelerator complex formation has been examined. Although the experimental results can give no direct evidence for the structure of the complexes, they do contribute to an elucidation of the complex formation in the vulcanization process.     

Unusual use of the term “differential scanning calorimeter”

Derivatograph was used to investigate pseudohomogeneous ion-exchange membranes. Two membrane types were examined: a) a membrane obtained from polyethylene film modified with the copolymer of styrene and DVB; and b) membrane AMF C-311 obtained on a film of fluorinated polymeric material.Although differential thermal analysis (DTA) has been used in the investigation of polymers only recently, a large number of papers concerning different problems in this field have already appeared. Only a few of these papers, however, have been devoted to cross-linked polyelectrolytes and more exclusively to ion-exchange resins [1–5], i.e. homogeneous polyelectrolytes. Up to date no publication dealing with pseudohomogeneous ion-exchange membranes has appeared. The pseudohomogeneous membrane is a system of two phases: a polymer film (polyethylene is most often used as matrix), with a cross-linked acid (e.g.polystyrenesulphonic acid) dispersed in the polymer film. The present investigation was undertaken to find the correlation between the thermal curves of a pseudohomogeneous cation-exchange membrane and the thermal properties of both phases of the membrane.The authors wish to thank T. Grodzicka, Institute of Chemistry, N. Copernicus University, Toru>n for determinations carried out with the MOM Derivatograph.     

A new technique of analysis for the investigation of kinetic data using the differential scanning calorimeter

This method of analysis for kinetic data of solid state chemical reactions takes advantage of the binomial series expansion to normalize various mathematical expressions related to various solid state models into a power series. This facilitates analysis by computer methods, in that deviations of the various models will be perceptible at the outset.     

Determination of heat of mixing and heat of vaporization with a differential scanning calorimeter

A simple method is presented for measuring the heat of mixing and the heat of vaporization of volatile liquids at temperatures below their boiling point. It consists in introducing liquids by a microsyringe into a nearly closed cell of the DSC. The relative standard deviation for 4 to 5 runs is ca. 5% for heat of mixing and ca. 2% for heat of vaporization.     

A study of the phase behaviour of metal-free phthalocyanine in a differential scanning calorimeter

The phase behaviour of metal-free phthalocyanine (H₂Pc) has been studied in a differential scanning calorimeter. The effect of the thermal history of samples on the DSC curves was investigated to obtain data concerning the phase transition which appeared on α as well as β forms of H₂Pc over the termperature range from 250 to 340 K. To characterize the α metal-free phthalocyanine at low temperatures, the capacitance of an Ag(H₂Pc)Al sandwich was measured as a function of the temperature. The specific heats of the α and β forms of H₂Pc and the heat of the α → β polymorphic transition were measured. Kinetic parameters of the α → β polymorphic transition have been derived from the calorimetric results.     

Thermal behaviors of electrolytes in lithium-ion batteries determined by differential scanning calorimeter

Lithium-ion batteries have been widely used in daily electric appliance, but abusive accidents occurred from time to time. Lithium-ion batteries composed of various electrolytes (containing organic solvents, inorganic salts), binder, and electrode materials, which may be unstable under some abnormal conditions. The formulation or components of electrolytes played a crucial factor in affecting reactive hazards within the cell. In order to meet safety requirements of the lithium-ion batteries on electronic device, reseachers and scholars are continuing to do further studies on the important issues in relation to the lithium-ion batteries. This study aims to apply the differential scanning calorimeter for measuring the thermal or reactive hazards of the organic solvents related to the formulation of the electrolytes. Besides, thermal instabilities of lithiated graphite or deposited lithium with electrolytes were simulated by the reactions between metallic lithium (Li) and organic carbonates of linear and cyclic structures. Exothermic onset temperatures and enthalpy changes were measured and analyzed. Results showed that the thermal behaviors of these organic carbonates themselves or with lithium hexafluorophosphate liberated less enthalpy changes. However, violent exothermic reactions were detected between the linear or cyclic carbonates and lithium metal with larger enthalpy change larger than 1,000 J g^?1 of lithium. This can be observed by Li reacted with diethyl carbonate at surprisingly lower onset temperature about 46.6 °C.     

Determination of thermodynamic properties of YRhO3(s) by solid-state electrochemical cell and differential scanning calorimeter

The standard molar Gibbs free energy of formation of YRhO₃(s) has been determined using a solid-state electrochemical cell wherein calcia-stabilized zirconia was used as an electrolyte. The cell can be represented by: ( - )\textPt - Rh/{ \textY₂\textO_\text3( \texts ) + \textYRh\textO₃( \texts ) + \textRh( \texts ) }//\textCSZ//\textO₂( p( \textO₂ ) = 21.21  \textkPa )/\textPt - Rh( + ) \left( - \right){\text{Pt - Rh/}}\left\{ {{{\text{Y}}_2}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right) + {\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right) + {\text{Rh}}\left( {\text{s}} \right)} \right\}//{\text{CSZ//}}{{\text{O}}_2}\left( {p\left( {{{\text{O}}_2}} \right) = 21.21\;{\text{kPa}}} \right)/{\text{Pt - Rh}}\left( + \right) . The electromotive force was measured in the temperature range from 920.0 to 1,197.3 K. The standard molar Gibbs energy of the formation of YRhO₃(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by: D_\textfG^\texto{ \textYRh\textO₃( \texts ) }/\textkJ  \textmo\textl ^{- 1}( ±1.61 ) = - 1,147.4 + 0.2815  T  ( \textK ) {\Delta_{\text{f}}}{G^{\text{o}}}\left\{ {{\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right)} \right\}/{\text{kJ}}\;{\text{mo}}{{\text{l}}^{ - 1}}\left( {\pm 1.61} \right) = - 1,147.4 + 0.2815\;T\;\left( {\text{K}} \right) . Standard molar heat capacity C^o_p,m C^{o}_{{p,m}} (T) of YRhO₃(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges from 127 to 299 K and 305 to 646 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: $ {*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ $ \begin{array}{*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ \end{array} The heat capacity of YRhO₃(s) was used along with the data obtained from the electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K.     

Determination of solidus and liquidus temperatures by means of a Perkin-Elmer 1B differential scanning calorimeter

A Perkin-Elmer 1B DSC apparatus was used to test the O'Neill expression for the melting interval of pure compounds on samples of organic compounds 1–10 mg in weight. On the basis of O'Neill's model, an expression for the melting interval of solid solutions,T, has been derived. The difference betweenT andT ₁ – T _s (T ₁ andT _s = =liquidus and solidus temperatures) is discussed. A simple procedure for the determination of solidus and liquidus temperatures from DSC data is proposed.

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Zusammenfassung Ein Perkin-Elmer DSC-Gerät 1B wurde zur Prüfung des O'Neillschen Ausdruckes für den Schmelzbereich reiner Verbindungen an Proben organischer Verbindungen von 1–10 mg eingesetzt. Auf Grund des O'Neill-schen Modells wurde ein Ausdruck für den Schmelzbereich fester Lösungen,T, abgeleitet. Der Unterschied zwischenT undT ₁ – T _s (T ₁,T _s =Flüssig- und Fest-Temperaturen) wird erörtert. Eine einfache Methode zur Bestimmung von Fest- und Flüssigphasentemperaturen aus DSC-Daten wird vorgeschlagen.

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1 — ' , 1–10 . ' . T -T , T _c — . .

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