The vapour pressure of cyclohexane over the whole fluid range determined using comparative ebulliometry

Vapour pressures of n-hexane determined by comparative ebulliometry

“…This value of p c is also in good agreement with the value measured directly by Brunner [15] and is well within the experimental uncertainty of the critical pressure recommended by Ambrose [16]. The coefficients of equation (5) [23] who covered the wide temperature range of (307 to 443) K, report vapour pressures in the band of +0.2% to À0.14% with respect to equation (5), and seven of their results for (393 to 423) K agree within 0.01%. At higher temperatures, (484 to 505) K, the results by Mousa [24] are [22]; , Sauermann et al [23]; À, Mousa [24]; }, Seo et al [25]; s, Bich et al [26]; j, Genco et al [27]; ·, De loos et al [28]; N, Oscarson et al [29]; +, Ida et al [34]; -,…”

“…Regression analysis with equation (4) now produced systematic deviations similar to those depicted in figure 1 for the forms with s 2.5 and s 5 or the form with s 3 and s 6 . We encountered this situation before when fitting the vapour pressures of cyclohexane [5], octane [6], acetonitrile [7], and n-heptane [20] and found that an additional term, statistically significant, was needed to account for the behavior at low pressures and to avoid these systematic deviations. Figure 2 shows the deviation plot of our final equation (5) which represents the experimental vapour pressures with standard deviations of r(p) = 26 Pa and r(ln p) = 42 AE 10 À6 .…”

“…At the time, we only measured the vapour pressures of n-hexane down to 41 kPa, although with this same equipment we have since measured vapour pressures as low as 5 kPa and obtained measurements that are of comparable quality to those measured in glass ebulliometers [5][6][7]21]. We have extended the low pressure region down to 13.8 kPa by selecting the vapour pressures measured by Rossini [22] using glass ebulliometers in the comparative mode; we have converted all RossiniÕs temperatures to ITS-90.…”

“…Triple distilled water was used as the reference fluid and helium as the buffer gas. The details of the apparatus have been published before and the reader is referred to the previous articles for a description [5][6][7].…”

“…The great majority of vapour pressures measured by the ebulliometric method have been restricted to pressures below 200 kPa through the use of glass boilers, but work with stainless steel vessels in different laboratories has extended the pressure range considerably in the last decade [4][5][6][7][8][9][10][11]. We report 54 vapour pressures of nhexane over the temperature and pressure range from (315.7 K, 41.1 kPa) to (504.0 K, 2876.8 kPa), which is about 3 K and 150 kPa below the critical point.…”