First, surfactants (as far as I know) always reduce surface tension. If the surface tension was stronger than normal, bubbles wouldn't form. Isn't that how they reduce foaming? I thought they introduced something that increased the surface tension.
Second, mercury is a really difficult substance to work with. I think people have gone over the EXTREME toxicity (i.e. causes brain and liver damage, absorbs through skin contact, is almost impossible to medically treat, and stays in the body forever). However, even if you can handle the mercury safely, it is still not easy to use. That is because mercury loves to combine with metal surfaces in what is called an amalgamation. So, you need to use coolant lines and heat exchange surfaces which are non-reactive with mercury (e.g. certain ceramics like glass).
Third, antifreeze is not a very good biocide. BigBen2k is correct, unfortunately! I have seen cars with some algae-like substance growing in the antifreeze overflow reservoir, so I knew that something was alive in there.
Fourth, I am really excited about two of the biocides being mentioned: sodium metabisulfate and erythromiacin (sp?). I'm wondering how stable those are over time and temperature. So, how often would you need to add it so the coolant? What are the byproducts of these substances as they degrade (i.e. would they form corrosive compounds or would they deposit inside the waterblock)?
This thread was what got me so excited that I wrote that article, btw. I was writing a reply that was getting too big so I finished it up with some research and gave it to Joe for posting. Good stuff being discussed here! Keep it up!
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