if you are doing immersion.
I would do this buy a blow torch go out doors on a concrete pad or a sandy area.
get a cup of your coolant (does not apply if you used distilled waterblock system )
put the cup of coolant in a stainless steel bowl
fire up the blow torch and see if the coolant burns.
some coolants are flammable and you do not want to use them to cool off 5000 watts of psu and
hashboards.
also test the coolant to see if it conducts electrical current on low levels it should not.
Good point!
The correct kind of liquid coolants for immersion cooling are typically PFPE (Perfluoropolyethers) such as Solvey Galden, which has a high dielectric strength (i.e. non conductive) is non flammable and non toxic.
Interesing side note, Galden PFPE is also used in vapour phase soldering for electronics.
IIRC its expensive depending on the temperature requirements.