What determines purity? It is possible (though unlikely) that an observed effect resulting from an experiment in chemistry could contradict established theories of physics. As long as the experiment stands up to a greater deal of scientific scrutiny than prior observations in physics which contradict it, physics must be ammended.
Define observation. By attempting to calculate the circumference of a circle using a similar shape with an increasing number of sides, it becomes apparent that the ratio of circumference (perimeter) to Diameter tends towards pi. Why is this distinct from a scientific observation?
The statement above does not appear in any challenges, supports, or specifications of other statements.