What else could account for our results? 1-The solu6ons of lac6c acid we used were not pure, since some water must be present for lac6c acid to be a liquid. The amounts of water in the two samples were slightly different, or their viscosi6es would have been iden6cal. The water concentra6on in the racemic must therefore be midway between those of the two enan6omers, and there could conceivably exist a local viscosity minimum. There is, however, no evidence of any anomaly in the monotonic viscosity vs dilu6on curves of lac6c acid . 2-The forma6on of a small amount of lac6c acid polymers affec6ng the viscosity cannot be ruled out, but it is hard to see how mixing them could yield the observed effect. 3-Differen6al effects of chirality on enan6omer drib in viscous flow are known , but none would lead to a low racemic viscosity even if some enan6omer separa6on occurred at the low shear values used in these experiments. In conclusion, the most parsimonious explana6on of the effect we observe is a decrease in intermolecular force similar to the one predicted by SDCR and seen in atomic force measurements . It may be possible to detect a reduc6on in hydrogen bond strength in racemates directly by vibra6onal spectroscopy . If its origin in SDCR is established, the anomalous viscosity of racemates would be a classroom demonstra6on of the first fluid-mechanical effect since superfluidity that requires a quantum mechanical explana6on.