Seven novel 3-alkyl (aryl)-4-(2-furylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) were synthesized in good Yields by the reactions of 3-alkyl (aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) with furan-2-carboxyl aldehyde. The newly synthesized 3 except compound 3c, were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents, including acetonitrile, methyl alcohol, isopropyl alcohol and tert-butyl alcohol. The half neutralization potential values and the corresponding pKa values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, N-acetyl derivatives of 3 were also prepared. The structures of thirteen new compounds were established by the elemental analysis. IR, H-1 NMR and UV spectral data.