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.