Some comments on the history of thermogravimetry

Abstract In a review of the authors about the history of vacuum microbalance techniques (including a chronology in table form), also published in Thermochimica Acta, (ref. 1) it uas pointed out, that also some corrections are to be made on the history of therinogravimetry. The first findings of balances are dated to about 3000 B.C. A gravimetric hygrometer is mentioned by Nicolaus Cusanus in 1450. In the 19th century chemical reactions at variable temperatures uere investigated using balances. The very beginning of the thermogravinietry is antedated to the work of Talabot who in 1833 at Lyon equipped a laboratory with thermobalances for quality control of Chinese silk.

Standardisation, Reference Materials and Comparative Measurements for Surface Area and Pore Characterisation

Summary This paper reviews current activities to standardise measuring procedures for surface area and pore size determination. Comparative measurements at different laboratories using candidate reference materials revealed that surfaces of highly dispersed materials can be affected remarkably during storing and sample preparation. On account of the fractal nature of these materials, the results depend on the measuring methods. Reference materials of dispersed materials are offered by national and international standardisation administrations and by industrial distributers. The standardisation of measuring methods becomes more and more international (ISO, IUPAC). The survey includes tables …

Fast Measurements of Adsorption on Porous Materials Using Jäntti's Method

In 1972, Jäntti et al. formulated a method to shorten the time taken for adsorption measurements. We suggested at the Kiev International Conference on Vacuum Microbalance Techniques (1999) that the applicability of this method could be widened by considering a number of parallel adsorptions. There is, however, a more complicated but perhaps more interesting variant possible when extra mass transport is considered to occur in series. Such an application could involve adsorption within a porous structure where diffusion must be considered as a process occurring in series with adsorption on the surface.

Investigation of characterizing methods for the microstructure of cement

Volumetric, gravimetric, calorimetric, flow methods, mercury porosimetry and laser granulometry were used to investigate the surface structure and the sorption behavior of industrial cements and hydrated cement paste. The suitability of the measuring methods is assessed.

Compensating isothermal calorimeter to investigate the vulcanization of factice

Abstract Sulphur factice is produced from a mixture of a vegetable oil and sulphur for linkage. To start vulcanization, the mixture is heated to temperatures betueen 130 and 150 °C. Within hours or days the temperature increases to about 160 °C and the product solidifies. To investigate the production process and to optimize the reaction, the temperature development was simulated in laboratory-scale experiments and the heat released was measured. In order to investigate the reaction kinetics of the entire vulcanization process, the calorimeter must a11ow the measurement of the mixture in liquid and solid state. The developed compensating calorimeter consists of a hot plate equipped with thi…

Standardization of sorption measurements and reference materials for dispersed and porous solids

Surface area, density and porosity measurements using the magnetic suspension balance

The advantage of gravimetry in the determination of surface area is discussed in comparison with the volumetric method. The magnetic suspension balance is described and new developments are presented. As an example of the application of gravimetric measurements the determination of apparent density and specific surface area before and after oxidation of a Poco graphite are described.

Investigation of surface properties of lunar regolith: Part I

This paper describes an initial investigation of the surface properties of three lunar soil samples from the Apollo 11, 12 and 16 missions, respectively. We report on density measurements using a helium pycnometer, adsorption isotherms of krypton applied for the determination of specific surface area of the samples and gravimetric measurement of the isotherms of water, heptane and octane. Electron-microscopic photographs are described and discussed.

The Determination of Mass: 3.5 Vacuum Weighing

The characterization of the capability of a balance

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.

Restoring of A balance by electric pulses

Restoring of the balance beam to its initial situation after a change of load can be effected by combination of forces of different kind. In former papers we discussed the possibility using the equation of motion of the balance to determine the mass to be measured. After the measurement the balance was restored by means of current pulses into the electromagnetic measuring system. In the present paper we discuss the application of electric pulses into an additional electrostatic system.

Some intriguing items in the history of adsorption

Abstract Clay was already used in antiquity as a drying and bleaching agent, a carrier for paints, and for various medical purposes. Sand was applied for water desalination. Charcoal was recommended as an antidote Based on Lowitz' discovery of the decolorizing effect in 1785, charcoal was used for the purification first of sugar. The patents of Ostrejko in 1900 opened the way for its industrial application. Already in the Bible we find the description of an adsorption experiment. The systematic research began 1773 when Scheele observed the adsorption of air by charcoal using a volumetric apparatus. The first adsorption measuring instruments were hygrometers as described by Nicholas of Cues …

Investigations on The Micro-Structure of Hardened Cement Pastes

Abstract Creep is a mechanical property, that has to be taken into account in the design of concrete constructions. Earlier studies showed that creep of concrete, among other things, depends on the relative humidity of the environment and on the type of cement used. The origin of creep lies in the hydrated cement paste, which is present between the aggregates. This paper, based on a thesis of H.H. Willems (ref. 1) deals with the relation between the creep behaviour and the microstructure of hardened Portland (PC) and Portland-blastfurnace cement (PBC) pastes. At several relative humidities shrinkage and creep experiments have been performed with thin-walled hollow cylindrical specimens. Nex…

VAKUUMWAAGEN Teil 1: Einleitung und Makrowaagen

Waagen, bei denen sich das zu wagende Gut im Vakuum befindet, werden als Vakuumwaagen bezeichnet. Makrowaagen sind fur Lasten von mehr als 100 g ausgelegt. Zum Vergleich von Masseprototypen ohne Auftrieb wurden Vakuum-Komparatorwaagen entwickelt. Grose Vakuumwaagen werden zur Molekulargewichtsbestimmung und zur Messung der Gasdichte verwendet. Fur chemische Untersuchungen unter reduziertem Gasdruck und zur thermogravimetrischen Analyse werden Vakuum-Analysenwaagen mit elektrischer Meswerterfassung eingesetzt. Zur Steuerung von Produktionsprozessen in kontrollierter Atmosphare dienen Wagezellen unterschiedlicher Bauart. Balances destined for weighing of goods in vacuum are labeled as vacuum …

Weighing Scales Manufacturers

The history of scales manufacturing and of some important existing scales workshops is summarised. A table presents the most important existing manufacturers and their company profiles.

The Jäntti approach to adsorption with increasing gas pressure

Jäntti introduced a method of calculating equilibrium adsorption from measurements where the pressure of the gas was varied in a stepwise manner. His aim was to shorten the time necessary for a given measurement. The method was applied to gas/solid systems in which simple adsorption processes occurred and where the number of adsorption sites was infinite. The present paper discusses the case where no adsorption is possible on an already occupied site (Langmuir isotherm) while the number of positions available for adsorption is considered limited. The advantages of using a gas pressure that increases linearly with time are evident for studies with this limitation. It is shown that such meas…

A Random Walk Through Fractal Dimensions. VonB. H. Kaye. VCH Verlagsgesellschaft, Weinheim/VCH Publishers, New York 1989. XXV, 421 S., geb. DM 138.00 (Broschur DM 64.00). - ISBN 3-527-26468-X/ISBN 0-89573-496-6

Progress in the standardisation of particle and surface characterisation

In 1999, we published a comprehensive survey of standards and certified reference materials for dispersed and porous solids. The present paper summarises and reports on new standards and proposals.

Modern vacuumbalances

Different types of vacuum balances have been developed corresponding to the various applications [ 1 ]:

Thermogravimetric and Sorption Measurement Techniques/Instruments

The survey covers commercially offered instruments for the determination of the surface structure of porous solids based on isothermal measurement of physisorption of inert gases and of thermogravimetric instruments. Basic assumptions, features and experimental uncertainties are compared.

Saving time when measuring BET isotherms.

The measurement of adsorption isotherms and the detn. of surface properties of a solid by means of the BET equation usually takes a lot of time as it involves measurement of several dynamic adsorption curves each at a given gas pressure. Two different timesaving approaches are suggested: (a) the beginning of a single dynamic curve is considered and (b) the beginnings of a no. of different dynamic curves is considered. Approach (a) is less time consuming than approach (b), where approach (b) yields more accurate ests. of the BET-parameters. A discussion is given of the possibilities of using the time saving procedure of Jaentti for the two approaches. [on SciFinder (R)]

Extension of the Applicability of Jäntti's Method to the Fast Calculation of Desorption Data

The time for sorption measurements may be reduced substantially by measuring several values at short time intervals at the beginning of a kinetic curve and extrapolating them to the equilibrium value. The method used by Jäntti for simple adsorption processes has been extended to complicated processes described by a second-order differential equation. A simulated example is provided.

Gravimetric measurement of water vapour sorption, moisture and dry mass

The gravimetric measurement of the moisture content of solids is discussed in comparison to other usual methods. Results of measurements of silica gel are reported. Furthermore, we inform on standardisation work.

Application of jäntti's method to volumetric adsorption measurements

Jantti introduced a method to calculate the adsorption equilibrium by measuring the actual adsorbed amount three times after a change to the gas pressure. By this method the experimental time for adsorption measurement can be considerably shortened. The procedure was developed for use in adsorption measurements where the adsorbed masses are directly measured with a balance. In the present paper we will demonstrate that the method is particularly useful in volumetric (manometric) measurements.

Mass and Gravity

The book starts with a survey on the development of the concept ‘mass’ and of theories of gravity, beginning with Greek’s ideas on mass, Galileo’s experiments, Newton’s laws and their extension by Einstein’s theory of relativity. Data from measurements of the gravitational force on Sun, planets and the Moon are presented. Kepler’s laws on moving masses in the gravitational field are discussed as well as new discoveries on the expansion of the universe. Fundamental interactions of particles and particle/wave duality are described. The Theory of Everything is mentioned. The definition of the international unit of mass is reported as well as alternatives like watt or voltage balance, counting …

Calorimetric investigation of the vulcanization of factice

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.

Documentation and Archiving

In this chapter a historical survey on the development of balances is presented, also in tabular form. The documentation of balance constructions in museums and literature is shown. The development of science museums, technical libraries, and societies which include balances is reviewed, and a list of museums which exhibit balances is given.

Indicator system and suspension of the old egyptian scales

Abstract Detailed analysis of drawings of both the death balance and scales of daily life together uith technical considerations suggest a triangular pointer perpendicular to the balance beam and a plummet suspended in front of the beam. The suspension was made using a rope or metal rings, the axis most probably piercing the beam horizontally.

Poröse Materialien - Kurze Vor- und Frühgeschichte

Holzkohle kann als erstes synthetisches Material der Menschheit angesehen werden. Holz- und Knochenkohle sowie oberflachenaktive Erden wurden schon in vorgeschichtlichen Technologien vielfaltig benutzt. Die systematische Erforschung poroser Adsorbentien beginnt 1773 mit Scheele, Priestley und Fontana. Zu Anfang des 19. Jahrhunderts war die Zuckerraffinerie die erste industrielle Nutzung, Ende des 19. Jahrhunderts wurde die grosindustrielle Fabrikation poroser Materialien aufgenommen und mit der Wende zum 20. Jahrhundert wurden viele neuartige porose Materialien synthetisiert und erforscht.

Berechnung der Fraktaldimension einiger poröser Feststoffe aus der Stickstoff-Adsorptionsisotherme

Some comments on the history of vacuum microbalance techniques

Abstract Based on the reviews of Behrndt, Iwata, Duval, Jenemann and Gast, we present a chronology of vacuum microbalance techniques in table form. The earliest discoveries of weights and balances are dated to about 3000 B.C. In the 19th century, balances were operated in vacuum for meteorological purposes. Thermogravimetry began with Talabot who, in 1833 in Lyon, equipped a laboratory with thermobalances for quality control of Chinese silk. At the beginning of the 20th century, microbalances were placed in high-vacuum apparatus.

A fast two-point method for gas adsorption measurements

Balances for Special Applications

Some special applications and the corresponding balances are described in detail: laboratory balances, micro balances vacuum balances, thermo balances, magnetic suspension balances, oscillators, metrological comparators, tensiometer, suspended particles and elementary charge, mass analyser, density determination, particle analysis, magnetic susceptibility, post office and coin scales, body scales, and gravimeter. Vacuum equipment for balances, thermogravimetry, sorptometry, hygrometry, and moisture determination, gravimetric measurement of reaction kinetics, surface tension, ion traps, pyknometry, dust and particle concentration, grain size analysis are described. Gravimetric measurement of…

High-resolution sorption studies of argon and nitrogen on large crystals of microporous zeolite ZSM-5

High resolution adsorption (HRADS) with argon and nitrogen at 77 K were performed on large crystals of zeolite ZSM-5 using a novel volumetric device. Multi-step isotherms for both adsorptives could be observed for the first time. The micropore filling was followed by low temperature microcalorimetry. Exothermic heats of adsorption were found to be correlated with steps in the adsorption isotherms. Based on results from atom-atom potential energy calculations (AAP) as well as from independent model building it is shown that 24 kinetic adsorbate molecules can be situated in a ZSM-5 unit cell. Localized adsorption is presented as possible filling mechanisms. Experimental results are reasonably…

Standardization of Methods for Characterizing the Surface Geometry of Solids

Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals.

Gravimetric characterisation of the surface properties of a porous drug carrier

The gas adsorption method is the most common means to characterise the topology of solid surfaces with regard to its use as an adsorbent. Adsorption isotherms are determined advanta-geously using a vacuum microbalance: Thermogravimetric techniques allow the observation of sample degassing and its optimization. The dry mass is determined in situ, the mass of gas adsorbed is measured directly and different gases can be used without calibration. From the isotherm the pore size distributions, specific surface area, fractal dimension and density can be derived. Commercially available gravimetric sorption apparata and vacuum balances as well as software for data evaluation are reviewed in tables.…

Balance as Symbol and Object of Art

The symbolic use of the balance is reviewed, covering mythology and religion, icons and arts, its use in astronomy and astrology as well as in literature and music. In Old Egypt many paintings show men’s height balances symbolically used for soul weighing. In Greece the fate balance was known. In the Roman Empire the symbolic use changed to justice fairness, and legitimacy of coins and this holds until modern time. In the Bible and the Koran fair weighing in trade are demanded. In the Book of Revelation the balance is symbol for misery. Michael archangel became guide of the deceased to the last judgement and weighed the poor sinner against his good deeds. In the witch balance the mass of th…