crown ethers 12-crown-4 (12c4), benzo-15-crown-5 (b15c5), 18-crown-6 (18c6), nitrobenzo-18-crown-6 (nb18c6) dibenzo-18-crown-6 (db18c6) and dicyclohexyl-18-crown-6 (dc18c6), dissolved in dichloromethane, are able to form oxonium-ion complexes in contact with aqueous sulfuric and hydrochloric acid solutions. this ability allows the transfer of cr(vi) oxanions from the acid media, through an orga...

introduction: the purpose of this study was to evaluate the effect of different solvents; carbonic acid (h 2 co 3 ), hydrochloric acid (hcl), chlorhexidine (chx) and sodium hypochlorite (naocl) on the surface hardness of mineral trioxide aggregate (mta) and calcium-enriched mixture (cem) cement. methods and materials: plexiglass molds were prepared and filled with angelus mta or cem cement and ...