Photo of <a href="https://en.wikipedia.org/wiki/Guaiacol" class="extiw" title="en:Guaiacol">Guaiacol</a>, pure in an Eppendorf tube
<a href="//commons.wikimedia.org/wiki/User:Rillke" title="User:Rillke">Rillke</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>