... 52% or K2O 50%), granular and powder. We can produce SOP(K2O50% or K2O52%) agriculture grade .Formula of potassium sulfate K2SO4 ... %minFree Acid(H2SO4)1.5%max 1.45%maxPH3-5 4.5Water Soluble100% 100%Heavy Metal0.01%max 0.002%Calcium0 ... heat, avoid insolation, sign with no moisture and no insolation. SOP(K2O52%)