Use a voltmeter and test it. that's what I've read... hope it's not just some stupid thing someone made up.
Want to test for electrolysis in your coolant? Here’s the simple test: Using a digital multimeter, set it to read 12 volts DC. Attach one of the test leads to the negative battery terminal and submerse the other end into the coolant. Rev the engine to 2,000 RPM and reads the voltage on the meter. Any reading over .3-.4 volts indicates that the coolant is conducting too much electricity. Either the coolant needs replacing or you have a grounding problem in the vehicle. If the coolant is fresh, check for poor ground connections between the engine and the firewall and the engine and the negative battery terminal. ©, Rick Muscoplat "
Put your negative probe to the negative post on your battery. You then place the positive probe in the neck of your radiator.
0.2 V to 0.5 V - antifreeze is still good
0.5 V to 0.7 V - antifreeze is borderline
0.7 V or greater - antifreeze is unacceptable.
Lower voltage reading means less lead,benzene, and metals have contaminated the antifreeze.
Maybe just do that test periodically.