Purity, n.
Etymology: [OE. purete, purte, OF. purté, F. pureté, from L. puritas, fr. purus pure. See Pure.]
The condition of being pure. Specifically: (a) freedom from foreign admixture or deleterious matter; as, the purity of water, of wine, of drugs, of metals. (b) Cleanness; freedom from foulness or dirt. "The purity of a linen vesture." Holyday. (c) Freedom from guilt or the defilement of sin; innocence; chastity; as, purity of heart or of life. (d) Freedom from any sinister or improper motives or views. (e) Freedom from foreign idioms, or from barbarous or improper words or phrases; as, purity of style.
Shades of meaning
Fernald has no entry of its own for purity; he lists it under virtue.
Where he writes about it:
Honor rises far above thought of the motto that "honesty is the best policy." Purity is freedom from all admixture, especially of that which debases; it is chastity both of heart and life, but of the life because from the heart. — from virtue