Experimental determination of the spinodal P-T-x surface for the system 2-butoxyethanolwater using the ‘PPICS’ apparatus

The PPICS (Pressure Pulsed Induced Critical Scattering) apparatus has been used in conjunction with the light scattering theory of Debye and Scholte to investigate the spinodal and binodal characteristics of the 2-butoxyethanol + water system in pressure-temperature-composition space. Data have been obtained at 2-butoxyethanol concentrations ranging from 17 to 40 wt%, and pressures up to 200 bar. Corrections were made to counter the effects of solution turbidity and background scatter. The trends observed were consistent with previous studies and the known phase envelope geometry. It was observed however that the system was particularly sensitive to the purity of the 2-butoxyethanol. Trends in the spinodal data obtained at 1 bar were observed to differ significantly from that published by Wenzel et al. (1980). Possible reasons for this discrepancy are discussed.