Solubility is not to be confused with the ability to 'dissolve' a substance, because the solution might also occur because of a chemical reaction. For example, zinc 'dissolves' (with effervescence) in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction.
All three kidney, liver and lungs purify the blood. The lungs help remove carbon dioxide, the kidneys remove water-soluble waste and the liver removes fat soluble wastes and many other impurities from the blood....ref:http://www.pharmainfo.net/answers/pharmaquestion/which-organ-purifies-blood.
Kidneys are the most important organs of the excretory system. The function of the kidney is to clean from the blood substances not needed in the body. The kidney is a complex filter, where active and passive mechanisms are involved as well as several complex control mechanisms.