The potassium–sodium binary phase diagram has the following invariant reactions: cooling at 6.9°C, + L Na2K wt.% Na 99 47 54 cooling at –12.6°C, L 􀀀 + Na2K wt.% Na 23 3 54 (i) Give the name of each of the above reactions. (ii) Make an approximate sketch of the phase diagram. (iii) Find the fraction of Na2K in a 33 wt.% Na alloy at –12.5°C.