AbstractSaturated (I, ROSO3Na) and unsaturated (II, R'OSO3Na) tallow alcohol sulfates, the disodium salt ofa‐sulfonated saturated tallow fatty acids (III, RCH(SO3Na)CO2Na), the sodium salt of the methyl ester ofa‐sulfonated saturated tallow fatty acids (IV, RCH(SO3Na) CO2CH3), and commercial tallow soap flakes (V) were compared, singly and in combinations, as built and unbuilt solutions in soft and hard water, with respect to foam height and detergency, using four different types of standard soiled cotton.Built solutions of combinations of the two most soluble detergents, II and IV, at concentration 0.05% total active ingredient plus 0.20% builder in hard water of 300 ppm, remained perfectly clear on standing for several months. Built solutions containing I or II had the best foaming properties. The presence of soap decreased foam height.Cloths A and B showed the detergency of built solutions to be in the order I=II>IV>III>V, and all combinations containing I or II were superior detergents. With cloth C, detergents ranked in the order I=II=IV>III>V, and many combinations containing I or II with IV were synergistic. Cloth D did not distinguish sharply between detergents in built solutions in hard water.In general, detergent systems containing tallow alcohol sulfates witha‐sulfo esters had the most desirable solubility, wetting, foaming, and detergent properties.