THE MOLYBDATE TEST FOR SILICA
The molybdate reactive silica test will only expose one, or possibly two, of the Si atoms in a chain of polymerized silica. This means that the molybdate reactive silica test will only measure part of the total silica that may be in solution. This phenomenon gives rise to the term "giant silica" and also to what many people consider colloidal silica. Since polymerized silica molecules can approach the size of a true colloid, “Giant” silica can still be (at least partially) removed by ion exchange as well as by relatively large pore size micro filters.