Weighing is a relatively slow process and often requires a considerable time within investigation procedures or production
processes. Measures for the speeding-up of weighing are discussed, two cases being considered:
1. If slow reactions are observed, the equilibrium value can be extrapolated from the mass change curve.
2. If the reaction is faster than the balance response, the damping device can be manipulated and/or the equilibrium value
can be calculated from the oscillating balance readings.
A survey is given on important standardized definitions by which the capability of balances may be characterized. Some modifications are proposed with regard to the use of mass sensors for the continuous determination of mass variations. An important supplement is the ‘relative resolution’ introduced by Jenemann. Optimum values are presented.
The short survey concerns the discovery of adsorbents and the measurement of the adsorptivity. In the investigation of adsorption
very sensitive instruments are needed, developed only recently. Two methods, however, are very old: the volumetric and the
gravimetric measurement of the adsorbed amount. In the Bible we find a thorough description of a volumetric adsorption experiment.
The systematic research began in 1773 when Scheele, Fontana and Priestley observed the adsorption of air by charcoal. The
volumetric apparatus of Brunauer, Emmett and Teller set the prototype for many instruments devoted to measure adsorption isotherms.
The first gravimetric adsorption measuring instruments were hygrometers, described by Nicholas of Cues in 1450, Alberti and
Leonardo da Vinci. In 1833 Talabot installed 39 drying balances in a Lyon laboratory for humidity control of raw silk imported
from China. In 1912 Emich described an electronic beam microbalance to investigate adsorption and a coil spring balance. Today
isotherms are measured gravimetrically by means of electro-dynamically compensating microbalances. Also oscillating systems
are being used which allow weighing down to the zeptogram region.
Jäntti published in 1970 a method to obtain equilibrium values at an early stage of gravimetric sorption measurements. In
former papers the authors criticised and extended that method. In the present work we discuss problems of its applicability
on practical measurements.
Sulphur factice is produced from a mixture of a vegetable oil and sulphur at temperatures between 130 and 160‡C. The slow exothermal vulcanization results in rubber-like elastomers. We have developed an isothermal calorimeter for measurements both in the liquid and the solid state and simulated the production process at the laboratory scale. The compensating calorimeter consists of a hot plate equipped with thin aluminium rods descending into a Dewar vessel. Besides optimization of the temperature control, remarkable savings of time were achieved by previous elaidinization of the oil using hydrosulphide.
The balance is the oldest real measuring instrument. It is still a widely used instrument in science, industry, commerce and
in the household. It has found significance as a symbol in religion, justice, commerce and as an esoteric object. As a balance
is always an interesting object it is exhibited in many museums and there exist a lot specialised scales-and-weight museums.
We attempt to give a survey of these.
One of the earliest measuring instruments used by human beings was the balance; evidence of this dates back more than 5.000
years. Initially, the weights of goods were measures rather of value than of mass. Besides yardsticks and graduated cups,
scales are today the most widespread instruments, found in almost all laboratories, factories and households. Indeed, the
balance accompanies us from birth to death.
The balance very early achieved a metaphorical meaning and was used for the comparison of ethical values. It first appeared
as an instrument in the death tribunal in Egyptian religion and later in Christianity. In the hands of the Grecian Gods, weighing
was a deciding factor as concerns victory or death. In Judaism and for the Romans, scales become the symbol of justice. Several
trade and handicraft guilds currently use the balance as an attribute, demonstrating in this way their sincerity and accuracy.
The balance is of dubious significance in astrology, as one of the signs of the zodiac.
This paper deals with the design of gravimetric apparatus with regard to the requirements of vacuum. Items discussed include
the calculation of suction speed and ultimate vacuum, the choice of the pump and of the method of pressure control, and the
design of the balance and the balance stand.