The effects of adding an antagonistic salt, sodium tetraphenylborate (), to a binary mixture of deuterated water and 2,6-dimethylpyridine were investigated by visual inspection, optical microscopy, and small-angle neutron scattering. With increasing salt concentration, the two-phase region shrinks. When the concentration of is , a temperature-induced lamellar/disorder phase transition is observed at 338 K. These trends are similar to those observed for a mixture of water/3-methylpyridine/ (Sadakane et al., Phys. Rev. Lett. 103, 167803 (2009)).