Mercury Penetraton and Retraction Hysteresis in Closely Packed Spheres

Abstract

Mercury penetratin, retraction, and scanning data are reported for random homogeneous sphere packings obtained with a low-pressure mercury porosimeter. Penetration and retraction in the toroidal region (Packing saturated with mercury, except at the contact points of the particles) was analysed using the theory of Mayer and Stowe. The observed hysteresis in this region was ascribed to contact angle hysteresis (6 – 8° hysteresis). When toroidal penetration was preceded by bulk emptying, void volumes in the toroidal region increased by about 10%. This was associated with the feeling of mercury from points of near contact (which remain closed during toroidal region scanning). Initial penetration or breakthrough is to be associated with the curvature of the menisci passing through the windows in the packing. Two models for calculating this culvature wewre considered (as they cannot be calculated exactly). Detailed interpretation of the mercury penetration awaits further development in the statistical description of random packings. Retraction and retention of mercury was analysed in terms of the curvature that is to be associated with the point where the anticlastic or pendular menisci merge when retreating from the contact points. Retraction, in general, will depende on the high-pressure point which determined the number of anticlastic menisci present. Attempts to describe the bulk hysteresis phenomena using the independent domain theory failed (as might be expected on the basis of a piori considerations). Domain function integrals evaluated from ascending and descending data over identical domains differed by as much as 1000%. it is not possible to obtain ‘ink-bottle’ pore distribution from scanning data.