Viscosities and Surface Tension of N, N' Methylureas in Aqueous Solutions Measured with Survismeter, a Novel Instrument

Viscosities (η, ± 0.06 × 10^-5 N s m^-2), surface tension (γ ± 0.05 × 10^-3 N m^-1) and densities (ρ ± 1 × 10^-2 kg m^-3) for 0.005 to 0.25 mol kg^-1 1-methylurea (MU), 1, 3-dimethylurea (DMU) and 1, 1, 3, 3-tetramethylurea (TMU) as N, N' methylureas at interval of 0.005 mol kg^-1 were measured at pH 7.99 to 7.01 and 293.15, 298.15 and 303.15 K temperatures. Intrinsic viscosities [η] and limiting surface tension γ⁰ are obtained from regression with molality, m. Contributions of -CH₃ (methyl) groups are derived from differences in [η] and γ⁰ values individually between their subsequent ureas. The [η] and γ⁰ values infer weakening of hydrophilic interactions with -CH₃ and strengthening of hydrophobic, and TMU shows structure making effect. As compared to measurements of viscosities and surface tension individually with viscometer and stalagmometer, the Survismeter minimizes 2/3rd of materials, human efforts and infrastructure with better accuracies. It prevents evaporation of liquids during surface tension measurements.