Decompression isotherms

After adjusting at a fixed pressure, no decrease in area per molecule was observed during several hours which indicates that the monolayers of our amphiphilic dendrimers are stable. Decompression isotherms of the monolayers showed irreversibility due to the formation of aggregates on the surface. The progressive increase of the surface pressure is probably due to the formation of films on the water surface that remain in the proximity of the platinum plate when the barrier is moved... 

Part of the liquid water introduced into the bomb in its standard state at 298.15 K is first isothermally decompressed from 0.1 MPa to its saturation pressure, psli, vaporized, and finally decompressed from psat to a negligibly small pressure (j> = ()). The corresponding changes of internal energy are... 

Figure 12. (a) Powder X-ray diffractograms obtained by isothermal decompression of VHDA... 

The dependence of the average excess pressure in foam (capillary pressure of bubbles) on its specific area is established by Derjaguin [105]. The mechanical work W done under isothermal compression (or decompression) of foam equals... 

This means that if the system is to maintain a constant temperature, the heat of reaction must be taken up by the heat of compression (or decompression). If the initial perturbation is an increase in pressure, then moderation will be observed only if the reaction induced in the system is such that the latent heat of decompression is supplied by the exothermicity of the reaction. The reaction must therefore be exothermal (hji j, negative), and at the same time be one in which the pressure decreases at constant volume pji y negative). If the reaction were endothermal, then isothermal conditions could only be maintained by a further increase in pressure. 

Figure 1. Hysteresis isotherm of polymer 3S on a water/air interface. The compression and decompression rate is 50 Mm/min.

The projections of the L(G) and Sp(L) isotherms in aP-Xcoi diagam (Fig. 3A) are almost vertical and parallel. As a consequence, the depressurization of a C02-supersaturated solution cannot perturb the fluid up to near-spinodal conditions gas exsolution will always proceed only by moderate bubble nucleations and any decompression process will be subspinodal. 

At T < Tc, LDL and HDL can be interconverted by, for example, isothermal compresslon/decompression, isobaric heating/cooling, or by following any thermodynamic path in the P-T plane that crosses the LLPT line (Fig. 1). As the LLPT line is crossed, coexistence of LDL and HDL occurs. From the thermodynamic point of view, the LLPT is analogous to the well-known LGPT the liquid and gas phases in the LGPT correspond respectively, to LDL and HDL in the LLPT. The order parameter in both phase transitions is the density difference between the two phases involved. At the LG first-order transition, liquid and gas domains coexist. Similarly, at the LLPT, LDL and HDL domains coexist. 

Inset of Fig. 3 shows that the oscillations in the P(V) isotherms vanish as T Tc-At T = Tc, the P V) isotherm has an inflection point, that is, (d P/dV )p = 0, which defines the coordinates of the LLCP Pc, Tc, Vc )- At T > Tc, LDL and HDL can be interconverted (e.g., by isothermal compression/decompression) but no phase separation occurs, the system remains as a single liquid phase. A natural question follows, how does the LLCP affect the liquid s properties at T> Tc Next, we address this question. 

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