H2SO4 in pyridine byproducts: H2, CaF2; Sonication; O2 and H2O excluded: H2(18)O added to CaH2 in pyridine, H2 evolution, reactn. mixt. stirred and sonicated (3d, room temp.), degassed, frozen (-196 ° C), TeF6 added (vac. transfer), heated and stirred (45 ° C, 12h), caution: TeF6-pressure!; pyridine and TeF6 removed (vac.), {pyH(1+)}{(18)OTeF5} extracted into warm CH2Cl2, CH2Cl2 removed (vac., white residue), (19)F NMR, concd. H2SO4 added, vac. distn., (19)F NMR;

sulfuric acid in water Cooling with ice;

H2SO4 in hydrogen cyanide