Everyday application for law of def. proportion?

<p>Can anyone think of an everyday application for the law of definite proportion/composition? I am stuck</p>

<p>well, a practical application, not necessarily an everday one. Any ideas?</p>

<p>rather a practical aplication for a principle disovered from the law. such as that reactions with products outside of the definite compound are less efficient than those that don't have anything left over besides the compound.</p>