Temperature calibration analysis experiment

Accurate temperature calibration using the ASTM temperature standards [131, 132] is common practice for DSC and DTA. Calibration of thermobalances is more cumbersome. The key to proper use of TGA is to recognise that the decomposition temperatures measured are procedural and dependent on both sample and instrument related parameters [30]. Considerable experimental control must be exercised at all stages of the technique to ensure adequate reproducibility on a comparative basis. For (intralaboratory) standardisation purposes it is absolutely required to respect and report a number of measurement variables. ICTA recommendations should be followed [133-135] and should accompany the TG record. During the course of experiments the optimum conditions should be standardised and maintained within a given series of samples. Affolter and coworkers [136] have described interlaboratory tests on thermal analysis of polymers. 

Radex Safety Calorimeter. The Radex calorimeter is a modular instrument that can simultaneously evaluate six different samples (size range 0.5 to 5 ml), or one substance under a variety of conditions. Each module is a separate entity with its own calibrated oven capable of being operated under an open, closed, or pressurized condition, with all temperature differences between the sample and the oven being stored in a microprocessor for further analysis. The Radex calorimeter is very versatile samples can be tested in either an isothermal or ramp mode. In the isothermal mode, each oven is heated to a preset temperature and held at that temperature throughout the experiment. In the ramp mode of operation, the oven is heated linearly to a preset temperature, or can be maintained at a given temperature for a predetermined time. The flexibility of oven function in the Radex calorimeter enables the user to determine the intrinsic stability of a chemical and to also compare the impact of such parameters as temperature, atmosphere, and impurities on the stability of a given substance. 

JOSEPH D. MENCZEL PhD. a recognized expert in thermal analysis of polymers with some thirty years of industrial and academic experience, is Assistant Technical Director at Alcon Laboratories. He has researched more than 120 polymeric systems in which he studied calibration of DSCs, glass transition, nucleation, crystallization, melting, stability, mechanical and micromechanical properties of polymers, and polymer-water interactions. Dr. Menczel holds six patents and is the author of seventy scholarly papers. He is the author of two chapters in the book Thermal Characterization of Polymeric Materials In conducting DSC experiments, Dr. Menczel found a crystal/amorphous interface in semicrystalline polymers, which later became known as the rigid amorphous phase. He is also credited with developing the temperature calibration of DSCs for cooling experiments,... 

This study presents kinetic data obtained with a microreactor set-up both at atmospheric pressure and at high pressures up to 50 bar as a function of temperature and of the partial pressures from which power-law expressions and apparent activation energies are derived. An additional microreactor set-up equipped with a calibrated mass spectrometer was used for the isotopic exchange reaction (DER) N2 + N2 = 2 N2 and the transient kinetic experiments. The transient experiments comprised the temperature-programmed desorption (TPD) of N2 and H2. Furthermore, the interaction of N2 with Ru surfaces was monitored by means of temperature-programmed adsorption (TPA) using a dilute mixture of N2 in He. The kinetic data set is intended to serve as basis for a detailed microkinetic analysis of NH3 synthesis kinetics [10] following the concepts by Dumesic et al. [11]. 

The procedure may start with the reference experiment, which, in the case under analysis, involved a solution of ferrocene in cyclohexane (ferrocene is a nonphotoreactive substance that converts all the absorbed 366 nm radiation into heat). With the shutter closed, the calorimeter was calibrated using the Joule effect, as described in chapter 8, yielding the calibration constant s. The same solution was then irradiated for a given period of time t (typically, 2-3 min), by opening the shutter. The heat released during this period (g0, determined from the temperature against time plot and from the calibration constant (see chapter 8), leads to the radiant power (radiant energy per second) absorbed by the solution, P = /t. ... 

The solvent-mediated transformation of o -L-glutamic acid to the S-form was quantitatively monitored over time at a series of temperatures [248]. The calibration model was built using dry physical mixtures of the forms, but still successfully predicted composition in suspension samples. Cornel et al. monitored the solute concentration and the solvent-mediated solid-state transformation of L-glutamic acid simultaneously [249]. However, the authors note that multivariate analysis was required to achieve this. Additionally, they caution that it was necessary to experimentally evaluate the effect of solid composition, suspension density, solute concentration, particle size and distribution, particle shape, and temperature on the Raman spectra during calibration in order to have confidence in the quantitative results. This can be a substantial experi-... 

Experience in this laboratory has shown that even with careful attention to detail, determination of coal mineralogy by classical least-squares analysis of FTIR data may have several limitations. Factor analysis and related techniques have the potential to remove or lessen some of these limitations. Calibration models based on partial least-squares or principal component regression may allow prediction of useful properties or empirical behavior directly from FTIR spectra of low-temperature ashes. Wider application of these techniques to coal mineralogical studies is recommended. 

Most hterature references to pharmaceutical primary process monitoring are for batch processes, where a model of the process is built from calibration experiments [110, 111]. Many of these examples have led to greater understanding of the process monitored and can therefore be a precursor to design of a continuous process. For example, the acid-catalysed esterification of butan-l-ol by acetic acid was monitored through a factorial designed series of experiments in order to establish reaction kinetics, rate constants, end points, yields, equilibrium constants and the influence of initial water. Statistical analysis demonstrated that high temperatures and an excess of acetic acid were the optimal conditions [112]. 

Vapor-liquid equilibrium experiments were performed with an improved Othmer recirculation still as modified by Johnson and Furter (2). Temperatures were measured with Fisher thermometers calibrated against boiling points of known solutions. Equilibrium compositions were determined with a vapor fractometer using a type W column and a thermal conductivity detector. The liquid samples were distilled to remove the salt before analysis with the gas chromatograph the amount of salt present was calculated from the molality and the amount of solvent 2 present. Temperature measurements were accurate to 0.2°C while compositions were found to be accurate to 1% over most of the composition range. The system pressure was maintained at 1 atm. 1 mm... 

The present work involves measurement of k in a 0.1 atmosphere, stoichiometric CH -Air flame. All experiments were conducted using 3 inch diameter water-cooled sintered copper burners. Data obtained in our study include (a) temperature profiles obtained by coated miniature thermocouples calibrated by sodium line reversal, (b) NO and composition profiles obtained using molecular beam sampling mass spectrometry and microprobe sampling with chemiluminescent analysis and (c) OH profiles obtained by absorption spectroscopy using an OH resonance lamp. Several flame studies (4) have demonstrated the applicability of partial equilibrium in the post reaction zone of low pressure flames and therefore the (OH) profile can be used to obtain the (0) profile with high accuracy. 

Fig. 11. Group contribution analysis leads to the determination of the effective area under the loss modulus-temperature curve. As in any spectroscopic experiment, background must be subtracted, and the instrument calibrated.

The experiments were carried out in a Netzsch STA 409 C (Simultaneous Thermal Analysis - STA) in the TGA/DSC configuration. The STA has a vertical san le carrier with a reference and a sample crucible, and in order to account for buoyancy effects, a correction curve with empty crucibles was first conducted and then subtracted from the actual experiments. Platinum/Rhodium crucibles were used in order to get the best possible heat transfer. The thermocouple for each crucible was positioned Just below and in contact with the crucible. The ten rerature obtained from the measurement is the temperature in the reference side. This temperature is converted to the temperature in the sample side by using the DSC-signal in pV and a temperature-voltage table for the thermocouple. The product gases were swept away by lOO Nml/inin nitrogen which exited the top of the STA, The STA was calibrated for temperature and sensitivity (DSC) with metal standards at each heating rate. 

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