✔ 最佳答案
When soap is dissolved in water which contain hardness of calcium bicarbonate . When the RCOONa + Ca(HCO3) to become (RCOO)2Ca which is insoluble in water . Therefore clear soap solution will become milky . But as distilled water there contain no calcium hardness the soap solution will remain clear . Soap is no good to be used as cleaning agent in hard water area .