Evaluation of glass dissolution vessel dimensions and irregularities

Abstract

This paper reports on studies of the geometric dimensions and irregularities in the surface of standard 1-L glass dissolution vessels. Eleven sets of six dissolution vessels from 10 commercial sources were selected for study. A three-dimensional coordinate measuring machine (CMM) was used to obtain results. The geometric dimensions studied were height, inner diameter of the cylindrical portion of the vessel, and radius of the hemispheric region. The following irregularities of the flange and of the internal surface of dissolution vessels were quantified: (1) flatness of the vessel flange,(2) roundness of the hemisphere at the base of the vessel, required to ensure smooth, unperturbed media flow, (3) cylindricity, roundness, and perpendicularity of the cylinder (i.e., the degree to which the walls of the cylindrical portion of the vessel were equidistant from a common axis, did not deviate from circular form, and were perpendicular to the common axis—in other words, how well this portion of the apparatus matched the characteristics of an ideal cylinder), and (4) concentricity between the hemisphere and the cylinder (i.e., the degree to which the axis of the cylinder aligned with the axis of the hemisphere, see Table 1 and Figure 1).Vessels from different sources displayed differences both for geometric dimensions and for surface irregularity measurements. Differences in hemisphere radius can result in as much as an 18% change in the volume of dissolution media surrounding the paddle. Measurements of cylinder and hemisphere roundness revealed as much as a 10-fold difference among vessels from different sources. Although differences were most noticeable among dissolution vessels from different commercial sources, differences among dissolution vessels from the same source were also observed.