The absolute (dynamic) viscosities (eta) and densities (rho) of carbonate-f
ree aqueous tetramethylammonium and alkali metal hydroxides have been deter
mined up to saturation concentrations ([NaOH] less than or equal to 19.1 M,
[KOH] less than or equal to 14.1 M, [LiOH] less than or equal to 4.8 M, [C
sOH] less than or equal to 14.8 M, and [(CH3)(4)NOH] less than or equal to
4.2 M) at 25.00 degrees C using a Ubbelohde viscometer and a vibrating tube
densitometer, respectively. The viscosities are believed to be precise to
within 0.1% and the densities to within 5 x 10(-6) g cm(-3). Densities of i
soplethic MOH solutions increase in the order of (CH3)(4)N+ < Li+ < Na+ < K
+ << Cs+. Viscosities for [MOH] < 4 M solutions increase in the reverse ord
er, but the viscosities of CsOH solutions become extremely large at very hi
gh concentrations. The shape of the density vs concentration function of (C
H3)(4)NOH solutions is also quite different when compared with the alkali m
etal hydroxide solutions. Density data were fitted up to the highest concen
trations using the Masson equation. Viscosity vs concentration functions ar
e represented in the form of a fifth-order (empirical) polynomial.