Beam microbalances

Balken,m. beam girder band (Anat.) corpus callosum, mikrowage,/. beam microbalance, -wage, /. beam balance. 

When using beam microbalances the effects due to buoyancy and thermal transpiration must be considered. The gas displaced by the sample produces a buoyancy force that reduces the weight by exactly the mass of... 

Czanderna, A, W and /. M. Honig Sensitive Quartz Beam Microbalance. Anal. Chem. 29, 1206 (1957). 

The method in brief is to suspend a thin sheet of metal or solid from the beam of a very sensitive, quartz beam microbalance operating in an all glass or ceramic ware vacuum system. The weight change of the specimen is followed continuously as various operations are performed upon it. When applied to the oxidation of metals these operations include evacuation to pressures of 10 6 mm. Hg or lower, degassing, preliminary reduction of the initial oxide film with pure hydrogen, and oxidation of the metal specimen under widely varying conditions of temperature and pressure. 

The simplest method of beam microbalance operation is to measure the deflection of the ends of the beam by optical magnification. This method has the disadvantage that the maximum weight change that can be observed is limited and the vacuum system must usuaUy be opened to reset the zero point. However, a beam microbalance can be readily converted to a null point instrument by electromagnetic adjustment. A commercially available instrument which features electromagnetic compensation and automatic recording is shown schematicaUy in Fig. 10. 

The rapid heating thermobalance employs a conventional single beam microbalance of the taunt-band suspension type. Maximum mass capacity is... 

Abstract The physical principles and experimental techniques of pure gas- and multicomponent gas adsorption measurements by the gravimetric method are outhned. Two beam microbalances and the magnetic suspension balance are considered. Several examples are given and uncertainties of data are discussed. Pros and cons of the gravimetric method are outhned. Lists of symbols. References. 

To determine the helium volume of NORIT Rl, sorption experiments with helium at 298.15 K and 323.15 K were performed using a two beam microbalance (Sartorius). Results of measurement are shown in Figure 3.9. The slope of the straight lines correlating data of the apparent weight of the sample as function of the density of the helium gas (pHe), is the negative value of sorbent s helium volume (V ), cp. eq. (3.13). 

Two beam microbalances have to be cooled during this process as their thermal range of operation normally is restricted to temperatures below 350 K. 

---