1973 Volume 1973 Issue 1 Pages 5-12
Various porous glasses were prepared by the extraction with HCI of borosilicate glasses (NazO 5 B20s, 12.7rSiO2), tchich was vafiotisly phase-separated by c6ntrolling the temperature and period of heat treatment. lsotherms of benzene sorption at OeC on the porous glass changed regularly in shape depending on the conditions of the pretreatment (Figs.1, 2, 3 and 4). Table 1 lists extracted fraction f (g!g) Qf each specimen, together with sorption characteristics obtained from BET plots and the isotherins. Analogous data from me. tnth. anol isotherms are given in Table 2. These results were discussed on the basis of capillary condensation theory. The shape of the benzene isotherm are different from that of methanol in some cases (Figs.5, 6), but pore distribution curves calculated from them agreed with each other except small difference in the very low pressure region. Figs.7 and 8 show that the theoretical condensation isotherms for the assembly of fine spheres arranged in the closest packing are in fair agreement with the experim. ental isotherms, when the granules of Jsepar-ate-d. pba-se a-r. e grgwn"up syfficignt, Ly. (ca: 5. ---t600 A in diameter). Volume of pore space ge calculated by f/2.20(1-f) is given in Fig.9by solid line and also in the last cQlumn of Table 1. Experimental values s asL, btained from the saturated amount of sorption as, are in agreement with thsO witl in 10%e of error for pecimens in which granules have grewn up sufficiently. Large deviations in Fig.9 are found with the specimens giving the type (1) isotherm and might be attributed to very fine pores possessing molecular-sieve effect for methanol as well as for benzene molecules. Thus, on the basis of capillary eoRdensation theory, it is concluded that regular change in isotherms is due te the growth of granules originated from silica-rich phase, and the pore space effective for sorption is formed by dissolution of the intergranular
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