<i>So people would use a mercury seal to put pressure on the water, allowing the system to run hotter without boiling.</i><p>I didn&#x27;t quite follow this part.  Where in the system does the mercury go, how does it add pressure, and does it have anything to do with Wikipedia&#x27;s description of using mercury in glass-to-metal seals?<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Glass-to-metal_seal#Mercury_seal" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Glass-to-metal_seal#Mercury_se...</a>