Ultrasound-enhanced grinding is a more practical alternative to glass bead-enhanced grinding for performing attrition-enhanced deracemization at large scale or in continuous flow. In this work, both ultrasound-enhanced grinding (41.2 kHz) and glass bead-enhanced grinding were applied to induce Viedma deracemization of sodium chlorate (NaClO 3) crystals in isothermal conditions. The results demonstrate that high intensity, low frequency ultrasound can achieve efficient grinding of enantiomorphous NaClO 3 crystals, producing small crystal size and narrow size distribution, both being highly desirable final product properties. Monitoring the width of the crystal size distribution, reveals its crucial role and offers further insight on the underlying phenomena in the deracemization process. Compared to glass bead-enhanced grinding, ultrasound-enhanced grinding resulted in faster crystal size reduction, and rapid initial deracemization. However, further increase in the enantiomeric excess was hindered after prolonged times of ultrasonication. This ensues probably due to the absence of crystal sizeinduced solubility gradients, owing to the existence of close to monodispersed sized crystals after the initial stage in the ultrasound-enhanced grinding process. We show that this can be overcome by combining: a) ultrasound with glass beads, or b) ultrasound with seeding, both of which led to enantiopurity.

A novel device is presented for direct measurement of the axial force evolution during the pinching of fluid filaments following an extensional step stretch, based on the 'tilted-CaBER'. The bending curve of the horizontally orientation fluid filament is fitted with the full expression of a catenary function, to directly and unambiguously extract the axial force from a single fitting parameter. The general limits of axial force determination from such devices are introduced in terms of a Bond number that accounts for the axial length scale.The new set-up is validated using a Newtonian PDMS oil, for which the axial force scaling and the related prefactors X of the similarity solution are known. For dilute polymer solutions in form of a Boger fluid, the so far theoretical factor X = 1.5 for an Oldroyd-B model fluid could be experimentally approached for the first time with the new setup.