Ebulliometer, differential

One of the critical issues in vapor pressure methods is the choice of the procedure to calculate the vaporization enthalpy. For instance, consider the vapor pressures of ethanol at several temperatures in the range 309-343 K, obtained with a differential ebulliometer [40]. The simplest way of deriving an enthalpy of vaporization from the curve shown in figure 2.4 is by fitting those data with the integrated form of the Clausius-Clapeyron equation [1] ... 

This paper describes an ebulliometric system for routine and special determinations of molecular weights. The system uses a simple ebulliometer, an immersion heater, and a Cottrell-type pump. Temperature sensing is by differential thermopile. Precision varies from about 1 to 6%, and values compare well with those from other laboratories and those from other methods. Values as high as 170,000 have been successfully measured. Some problems encountered in using the ebulliometric method are selection and effect of reference temperature, limitations of the vapor lift pump and a possible substitute for it, measurement of equilibrium concentrations within the operating ebulliometer, and the experimentally determined ebulliometric constant and some factors which influence its value. 

As pointed out above, dynamic vapor-hquid equilibrium measurement mediods are not very suitable for concentrated polymer solutions, especially due to their heavy foaming behavior. For dilute polymer solutions, however, diere is continuing apphcation of ebulhomelry as an absolute method for the direct determination of die number-average molecular mass M . Dedicated differential ebulliometers allow the determination of values up to an order of 100,000 g/mol. Ebulliometry as a mediod for molar mass determination was recently reviewed by Cooper, Glover, and Mays and Hadjichristidis. ... 

Figure 1.65 illustrates a differential ebulliometer for the measurement of boiling point elevations. This ebulliometer gives the precision which is required for... 

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