Vapor dilution apparatus, measurement

Figure 3. Vapor dilution apparatus to measure responses of coated electrodes.

The first of these is so small that it would be hard to measure precisely. Even this small lowering of the vapor pressure is sufficient to raise the boiling point by an amount that could be measured, although with difficulty. The freezing point depression is greater, but still could not be measured very precisely without a special apparatus. The osmotic pressure, on the other hand, is so large that it could be measured much more precisely. Thus, osmotic pressure is often the most easily measured of the four colligative properties, especially when very dilute solutions are used. 

Any physiological fluid such as plasma, saliva, urine, or breath water vapor can be collected for the determination of fractional turnover rates of and and JVh and Nq. In most human studies, urine is the preferred sample because it is noninvasive and the easiest to collect. In infants, urine can be collected using cotton balls (Wong et al, 1993a). The urine absorbed by the cotton balls can be expressed with a plastic syringe into an appropriate sample vial. If the samples are not processed immediately for isotope ratio measurements, they should be stored at —20 C until ready for analysis. The sample collection apparatus must be free of moisture in order to avoid dilution of the samples, particularly when only small quantities are available. 

Roper, V. Kohayashi, R. Apparatus and procedure to measure binary total pressure at high temperature fluorene - phenanthrene vapor-liquid equilibria and data reduction by the four-suffix Margules model to obtain infinite-dilution activity coefficients Fluid Phase Equilib. 1989,47, 273-293... 

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