Modifies a noun

• compound: Care should be taken using quaternary ammonium compounds in soft water.

• salt: To get mainly the quaternary ammonium salt, you can use a large excess of bromoethane.

• structure: They form parallel arrays to make larger, stronger quaternary structures called fibers.

• study: This is due largely to new dating methods which are now providing a firm basis for quaternary studies.

• center: He demonstrated the important effects arising from quaternary centers in polymer chains.

• level: Quaternary structure Not all proteins have a quaternary level of structure.