The basic principle of comparing the sample
mass with the mass of a reference body in equilibrium gives the equal-armed
beam balance a unique accuracy. Main parameters characterising the suitability
of the instrument are measuring range, resolution and relative sensitivity
(resolution/maximum load). The historical development of the values of these
parameters achieved depended strongly on the practical need in those times.
Technically unfavourable scales of the oldest Egyptian dynasties (~3000
BC) could resolve mass differences of 1 g and had a relative sensitivity of
at least 10–3. More sophisticated instruments
from the 18th Dynasty (~1567–1320 BC) achieved
a relative sensitivity of 10–4 independent
of the size of the instrument. In 350 BC Aristotle clarified the theory of
the lever and at about 250 BC Archimedes used the balance for density determinations
of solids. The masterpiece of a hydrological balance was Al Chazini’s
'Balance of Wisdom’ built about 1120. Its relative sensitivity
Real progress took
place when scientists like Lavoisier (1743–1794) founded modern chemistry.
At the end of the 19th century metrological balances
reached a relative sensitivity of 10–9 with
a maximum load of several kilogrammes. That seems to be the high end of sensitivity
of the classical mechanical beam balance with knife edges. Improvements took
place by electrodynamic compensation (Emich, Gast).
In 1909 Ehrenhaft
and Millikan could weigh particles of 10–15
g by means of electrostatic suspension. In 1957 Sauerbrey invented the oscillating
quartz crystal balance. By observing the frequency shift of oscillating carbon
nanotubes or of silica nanorods, masses or mass changes in the attogram or
zeptogram have been observed recently.
Specific surface area and pore size distribution are determined usually from adsorption isotherms at low temperatures using
nitrogen or noble gases. These are not absolute parameters and the measuring methods are fraught with serious difficulties.
General problems of sorption measurements and recent developments are discussed. To obtain information for practical purposes
these measurements need to be supplemented by investigations of the sorbate/sorbent system used in practice. Results of the
measurement of nitrogen and water vapour adsorption on different materials are compared.
Authors:A. Przepiera, K. Przepiera, M. Wisniewski, and W. Dabrowski
The thermal behaviour and phase composition of mixed oxides obtained by oxidation of iron(II) hydroxide in the presence of
Mg, Zn, Co, Cu and Ni, is investigated by thermogravimetry, and conventional and high-temperature X-ray diffractometry.
Authors:A. Przepiera, M. Wisniewski, W. Dabrowski, and M. Jablonski
Results of calorimetric determination of integral enthalpies of solution of some hydrates (monohydrates and heptahydrates)
of 3d transition metal sulphates such as FeSO4, NiSO4 and MnSO4 in three-component systems at sulphuric acid concentrations up to 2M are reported. Measured values of integral enthalpies of solution are the basis for calculation of activity coefficient temperature
dependences according to Pitzer's model.
Authors:A. Dąbrowski, E. Mendyk, E. Robens, K. Skrzypiec, J. Goworek, Mariola Iwan, and Zofia Rzączyńska
We investigated lunar regolith collected during the Apollo 11, 12 and the Apollo 16 missions. The Apollo 11 and the Apollo
12 samples come from the lunar mare, whereas the Apollo 16 expedition brought back material from a highland region of the
near side of the Moon. In paper series we summarise in brief the results of measurements using photoelectron spectroscopy
(XPS), Raman spectroscopy, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), nitrogen adsorption, thermal analysis
(TG, DTA) and temperature-programmed reduction and oxidation (TPRO) method. Parts of samples were examined by means of scanning
electron (SEM/EDS) and atomic force microscopy (AFM).