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.
The spleen is indeed an lymphatic organ. This however does not filter lymph it filters blood. Within the stroma of the organ lies all the different white blood cells, and indeed it is part of our immunity. The spleen does not produce blood, but it is the primary site of red blood cell destruction the liver being the second. Your spleen creates blood and fights infection. It belongs to your lymphatic system.