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To examine the relation between solution and soil redeposition in dry cleaning, we chose 5 different cleaning-houses where perchloroethylene is used as solvent with the washing attached by a white cloth and other various fabrics soiled by carbon black, such as cotton, wool, polyester, and acrylonitrile, and again 5 different cleaning-houses where petroleum is used. From Oct., 1973 to Mar., 1974 we pursued our examinations of the actual conditions of these cleaning-houses. As regards the kinds of cloths and their redeposition, a generalization can not be made because there are various factors that must be considered, but a comparatively high degree of soil redeposition was acknowledged in the case of cotton and acrylonitrile. As regards various kinds of cloths and their detergent efficiency, detergent efficiency was high in wool and was remarkably low in acrylonitrile. As regards the relation between degree of soiling and detergent efficiency, we could see that there are two classes of cleaning-houses, That is, (1) the kind where the degree of soil redeposition is low and detergent efficiency is high, and (2) the kind where the degree of soil redeposition is low and detergent efficiency is also low. We conclude therefore that the examination of the degree of soiling must always be accompanied by that of the relation between it and the solution.

Experiments were carried out with various fabrics to study both detergency and redeposition of dirts using Ferric Oxide mixed in water as model soils. The examined fabrics were cotton, polyester and poly-propylene. The results were as follows, (1) The examined fabrics dipped in water (H_2O) with Ferric Oxide were easily soiled in order of polypropylene, polyester and cotton. This results showed the reversal of the order of the consequence examined in CCl_4 with Fe_2O_3. (2) The detergency for cotton and polypropylene were a good efficiency, while polyester was inefficient.

In order to stuby the redeposition of ferric oxide and of carbon black, experiments were carried out with three kinds of synthetic fabric, nylon, polyester, polypropylene and with solution of surface-active agents, sodium dodecyle sulfate (S.D.S.), polyethylene nonyle-phenyl ether (E.P.O.). And in this cace four kinds of water which differed in hardness were used. The results were as follows : (1) The redeposition rate of Fe_2O_3 and of carbon black increased in proportion to the concentration of active agent, S.D.S. when nylon was used. In the case of polyester and polyplopylene, on the other hand, the lowest rate of the redeposition was recorded when the concentration of S.D.S. was at 0.2%. And the amounts of redeposition were remarkable in the case of each synthetic fablic in proportion as the concentration of active agent, E.P.O. was increased. (2) The redeposition rate of Fe_2O_3 and of carbon black was more influenced by th hardness of water in the solution of E.P.O. than in that of S.D.S.. And amounts of redeposition of carbon black were more susceptible to influences from the hardness of water than from those of redeposition of Fe_2O_3. (3) When the concentration of active agents, S.D.S., E.P.O., was strong the dispersion of carbon black was active. And when the hardness of water in the solution of S.D.S. and in that of E.P.O. was increased the dispersion of carbon blcak was inactive. In carbon black the disperting action was relative to the redeposition.