An interesting chart. I did a quick test of how the MCW6000 behaves with increasing proportions of coolant additive.
I have no idea of the exact properties of this, it is simply automotive antifreeze, ethylene-glycol. I have included standard deviations to give an idea of the noise levels. They are quite high, I did not spend too much time on this.
I will now definitely need to do some flow rate tests to try and establish the new Cp.
Tested with the Hydor S30 (a lower, more controllable flowrate to save spraying antifreeze all over my desk). Premixed by tapping off some of the water already in the loop and re-adding the solution to the reservoir. There is undoubtedly some inaccuracy due to insufficient mixing. Take it or leave it.
Attached some numbers vs flowrate.