1.0 0.5 0.0 FWHM(nm) 10 5 0 Pressure (GPa) (b) Vaselin R.T 77 K 1.0 0.5 0.0 (a) Silicon oil R.T 77 K 1st. 2nd. 1st. 2nd. FIG. 3: (Color online)Pressure dependence of full-width at half maximum (FWHM) of the ruby R$_{1}$ luminescence line at room temperature and 77 K for (a)silicon oil (polydimethyl- siloxane) and (b) Vaseline. C. Group III: 1:1 mixture of n -pentane and isopentan, 4:1 mixture of methanol and ethanol, petroleum ether, nitrogen, argon and helium. B. Group II: 2-propanol, glycerin and Daphne 7474 4 transmitting medium in high pressure studies. The hydrostatic-limit pressure of 2-propanol was determined to be 4.2 GPa by the ruby fluorescence method at room temperature [10]. The trivalent alcohol of glyc- erin (glycerol, C 3 H 5 (OH) 3 ) has been used mainly for medical purposes but also in the high-pressure studies for a long time [35, 36]. Osakabe and Kakurai pointed out that glycerin is the most suitable pressure-medium for use in neutron scattering experiments under high pressure up to 7 GPa [12]. There have been no re- ports on the hydrostatic-limit pressure of the glycerin medium. Daphne 7474 is a transparent and chemically non-reactive medium recently developed by Murata et al. [37]. The solidification pressure of Daphne 7474 was reported to be 3.7 GPa at room temperature. Figures 4 (a), (b) and (c) show the pressure de- pendences of the FWHMs for 2-propanol, glycerin and Daphne 7474 at room temperature and 77 K. At room temperature, the FWHMs for 2-propanol and Daphne 7474 start to increase roughly above the solidification pressures [10, 37]. The FWHM for the glycerin medium starts to increase above 5 GPa, which roughly corre- sponds to the solidification pressure at room tempera- ture [38]. This suggests the hydrostatic-limit pressure to be about 5 GPa at room temperature. At 77 K, the FWHMs of the three types of media show differ- ent pressure dependences. The FWHMs for 2-propanol and Daphne 7474 weakly increase in the low-pressure re- gion below 5 GPa but then strongly increase above the pressure. The pressure dependence of the FWHM for the glycerin medium shows a complex behavior: it in- creases non-linearly below 1 GPa, shows a tendency to saturate above 2 GPa, and then strongly increases again with increasing pressure above 5 GPa. The values of the ΔFWHMs for the three media are less than 0.2 nm at 5.0 GPa, significantly smaller than those of the media in Group I. However, the values of the ΔFWHMs at 10 GPa are comparable with those of the media in Group I. The value of the FWHM with glycerin is larger than those of some of the media in Group I, for example, Daphne 7373 and silicon oil, below 2 GPa, thus sug- gesting the strength of the nonhydrostatic effects with the glycerin medium to be larger than those of the two media. This is consistent with a previous evaluation of pressure-media by the $^{63}$Cu-NQR spectra of Cu 2 O at 4.2 K [15]. However, there have been no reports on its suitability as a pressure-medium as far as is known. Figure 3 (a) and (b) show the pressure dependences of the FWHMs with silicon oil and Vaselin at room tem- perature and 77 K. The FWHMs start to weakly increase above 3 GPa. The ruby R 1 lines for the media do not show a strong broadening effect at 10 GPa, thus indicat- ing weaker nonhydrostatic effects of the media compared with those of the former media. Previous studies have pointed out that silicon oil is as good a pressure medium as the 4:1 mixture of methanol and ethanol up to 20 GPa at room temperature [33, 34]. However, a small but fi- nite broadening effect does appear above 3 GPa, thus suggesting the pressure-quality of the silicon oil to be lower than that of the 4:1 methanol-ethanol mixture. At 77 K, the FWHMs for the media increase rapidly with increasing pressure above about 1 GPa. The value of the ΔFWHMs for the media at 10 GPa is about 0.5 nm, comparable with that of NaCl. We firstly show the results of the 1:1 mixture by vol- ume of n -pentane and isopentane (pentane mixture), the 4:1 mixture by volume of methanol and ethanol (4:1 M- E mixture) and the petroleum ether. The pentane and 4:1 M-E mixtures have been widely used in high-pressure studies for a long period of time [10, 39]. The hydrostatic- The secondary alcohol of 2-propanol (Isopropanol: CH 3 CH(OH)CH 3 ) has been accepted as a good pressure-