The water from a well is always the best water and does not require purification.

Experimental analysis of proteins typically require expression and purification of proteins.

The document explains that the church is holy, but is stained by the sins of its children, and requires "constant purification."

Generally, a one-step synthesis (method involving only one reaction) is used which does not require purification.

On trips over a day, or in especially hot conditions, need for more water than is carried may require purification of local water.

If this area is maintained well the water will require little purification before it enters the cistern.

Water may require purification for human consumption.

Object, location, and performer may require purification beforehand.

The resulting gas contains significant amounts of byproducts and requires purification.

These weapons, however, require purification after being used to slay a Horror.