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I. INTRODUCTION Liquid detergents provide convenience in our daily life ranging from personal care of hand and body cleansing and hair cleaning and conditioning to home care in dishwashing and cleaning of various household surfaces to fabric care in laundering and fabric softening. Compared with powdered detergents, liquid detergents dissolve more rapidly, particularly in cold water, they generate less dust, and they are easier to dose. It is not surprising, therefore, that liquid forms of cleaning products have been gaining in popularity since their introduction in the late 1940s.

I. INTRODUCTION Light-duty liquid detergents (LDLDs) are mixtures of surfactants dispersed in water and, as opposed to heavy-duty liquid detergents (HDLDs), are free of builders or alkaline inorganics. They are used primarily for hand washing of dishes, glasses, pots and pans, and other cooking and serving utensils. They are also usedfor washing hands, cleaning kitchen countertops, cutting boards, stove surfaces, and less often for washing delicate fabrics and general household cleaning.

I. INTRODUCTION Liquid soap was first developed in the 1940s and was primarily used in hospitals and institutions for washing hands. In the late 1970s with the launch of Softsoap brand liquid soap in the U.S. by Minnetonka, Inc., liquid soap has gained increasing popularity. Liquid soaps offer convenience and are considered to be more hygienic than bar soap especially in public places.

I. INTRODUCTION The concept of using mechanical devices for dishwashing was documented as early as 1865 with the issuance of a U.S. Patent to J. Houghton [1]. Subsequently several companies tried to manufacture and market automatic dishwashing machines for home as well as for institutional use [2,3]. However, it was not until the early 1950s that both detergents and mechanical dishwashers became widely available to consumers. By the early 1990s, an estimated 50% of the households in the U.S., 25% in Europe, and 8% in Japan had automatic dishwashers [4].

Water contact angles and contact angle variation with temperature on chemically modified glass microscope slide surfaces are given. A contact angle measurement technique for obtaining data from the diameter of known volume drops is described. Adhesion energies are calculated and adhesion entropies estimated.

This experimental study of the collection efficiency of freely falling water drops for AgCl aerosol particles in nitrogen extends earlier work (Kerker and Hampl, 1974) to submillimeter drop radii. In this case it was not necessary, as in the earlier work, to extrapolate to conditions corresponding to terminal velocity. The results are used to calculate washout coefficients for some hypothetical rainfalls, and they indicate that a significant fraction of the submicron aerosol may be removed by washout. In addition, the effect of charging the drops (for drop radii A = 0.62 and 1.82 mm) was measured. Five-fold increases in collection efficiency were obtained for surface charge densities in the range 2 to 9 × 10−10 C cm−2 which would indicate that there may be substantive increases in scavenging due to charge effects such as encountered in thunderstorms.