Adiabatic compressibility of biphasic salt melts

The adiabatic compressibility along the two-phase saturation line was calculated for nine molten immiscible mixtures, namely, LiF + KBr, LiF + CsCl, LiF + RbBr, LiF + KI, LiF + CsBr, LiF + RbI, LiF + CsI, LiCl + AgBr, and NaCl + AgI, using experimental data on the sound velocity and density. It is shown that the ratio of compressibility of the equilibrium phases depends significantly on the sizes of the mixed ions. The dependence of the changes in compressibility in the distance and in the vicinity of the critical mixing point on the characteristics of the chemical bond between the ions is discussed.

Liquid immiscibility in fluid–magmatic systems: an experimental study

Liquid immiscibility was studied in melting experiments in the system trachyrhyolite–water + salt (NaF, Na2CO3) conducted at parameters imitating those of the volcanic process. The indicator components were La, Nb, Sr, W, Mo, Cr, Fe, Rb, and Cs. The experimental runs were carried out in a high gas pressure apparatus. At 1200oC and 5 kbar, melting, homogenization, and melt saturation with fluid components occurred. A decrease in the P-T parameters to 1000°C and 1 kbar led to the onset of liquid immiscibility in the form of droplets in the melt matrix. The composition of the droplets is similar to that of the melt matrix and differs from the latter only in concentrations of water, indicator components, and proportions of alkaline and alkali-earth elements. In the presence of salt (NaF), the melt exsolved into immiscible silicate and salt melts. No liquid immiscibility was detected when Na carbonate was added to the melt, but its agpaitic coefficient increased.