The technological condition of Potassium Sulfate production from impure glaserite and impure Potassium chloride, is discussed in the paper,It is proved by experiment.
Although impure liquid hydrazine doesn't explode, it can certainly boil vigorously and spray hot and chemically toxic liquid around, which can endanger the safety of people nearby.
In 1908, Harvey Wiley, who was then the head of the US Food and Drug Administration, sought to have saccharin eliminated from the food supply as an impure additive.