Search Results

You are looking at 1 - 10 of 3,443 items for :

  • Chemistry and Chemical Engineering x
  • All content x
Clear All

data of the standard molar enthalpy of formation plays an important role in theoretical study, application development and industrial production of a compound as a basis of theoretical analysis. In this article, ZnO nanosheets with uniform size

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Eveline De Robertis, Gabriela F. Moreira, Raigna A. Silva, and Carlos A. Achete

for thermal behavior studies, since by the standard method for such determinations the major drawback is the time of analysis. In this work, our intention is verify the thermal behavior of two standard reference materials (SRM) using DSC, such

Restricted access

connected to a Wheatstone bridge and recorded versus time. Chemical calibration of the device was carried out by a standard reaction [ 11 ]. Experiments consist in dissolving various amounts of trihydroxymethyl aminomethane (HOCH 2 ) 3 CNH 2 or

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: B. Coursey, J. Hutchinson, L. Lucas, W. Mann, T. Matsumura, and J. Noyce

Abstract  

The low-level radioactivity laboratory in the Radioactivity Section of the National Bureau of Standards, and its work in producing standards for monitoring in the environment, are described.

Restricted access

Abstract  

The availability of natural matrix reference materials evaluated for trace element content has resulted in their widespread use as standards (i.e., calibration materials; comparators) for instrumental neutron activation analysis (INAA). Due to the uncertainties associated with their certified values, the limited number available, and the relative matrix independence of INAA, these reference materials are more properly utilized as quality assessment materials, after calibration of the INAA analytical system with true primary standards. Terminology is defined, the use of matrix reference materials to evaluate the analytical system is discussed, techniques for the accurate preparation of primary standards for trace element analyses are reviewed, and necessary precautions in the accurate comparison of samples to standards are presented.

Restricted access

Abstract  

Using instrumental neutron activation analysis 18 elements are determined in 9 standard rocks of the central geological institut of the GDR. The results are compared with certified values.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: P. Gallagher, R. Blaine, E. Charsley, N. Koga, R. Ozao, H. Sato, S. Sauerbrunn, D. Schultze, and H. Yoshida

Abstract  

Magnetic transition temperatures, Tc, are measured by simultaneous TM/DTA for Alumel, cobalt, nickel, and three alloys of Ni and Co. The observed values of Tc are corrected using the values for the melting temperatures of pure metals used to define the International Temperature Scale. These corrections are based on the simultaneous melting of these pure metals alongside, but separate from, the magnetic sample. Nine investigators, using a wide variety of instrumentation, have made these measurements utilizing a standard protocol. The results are compared for several heating rates. It is planned to make these same magnetic materials ultimately available to the public for calibration of temperature of their TG instruments.

Restricted access

Abstract  

Stoichiometric, stable fluorides for comparison standards in neutron activation analysis were prepared by horizontal zone-refining or sublimation in HF atmospheres. The fluorides of Na, Mg and Al were shown by thermogravimetry to be anhydrous and to remain water-free after exposure to room air. Fluorine in the purified samples was separated by the pyrohydrolysis method and subsequently measured by acid-base titrimetry or selective ion electrodes. Deviations from theoretical values were ±0.1, ±0.9 and ±2.8% respectively for fluorides of Na, Mg and Al.

Restricted access

pure substance were determined by a precision oxygen bomb calorimeter. Then the standard molar enthalpies of combustion and formation were calculated by thermodynamics principle. So the related studies can provide a thermodynamic basis for taurine

Restricted access

specific surface area, density, and chemical activity. In our previous papers [ 8 ], some metal phosphates, e.g., NH 4 MPO 4 ·H 2 O (M = Mn 2+ , Co 2+ , Ni 2+ , Fe 2+ , Zn 2+ , Cu 2+ ), have been prepared by solid-state reaction. Their standard molar

Restricted access