EFFLORES'CENCE, noun In botany, the time of flowering; the season when a plant shows its first blossoms.

1. Among physicians, a redness of the skin; eruptions; as in rash, measles, small pox, scarlatina, etc.

2. In chimistry, the formation of small white threads, resembling the sublimated matter called flower, on the surface of certain bodies, as salts. This is properly a shooting out of minute spicular crystals, called sometimes a saline vegetation, as that of the sulphate of magnesia on the deserts of Siberia, and of natron in Egypt. In butter much salted, the salt shoots in spiculae, and an efflorescence is often seen on walls formed with plaster. In some species of salts, as in sulphate and carbonate of soda, the efflorescence consists of a fine white dust. This kind of efflorescence is the contrary of deliquescence. In the latter, the saline crystals decompose the air, or rather abstract moisture from it; in the former, the atmosphere decomposes the saline crystals, and the water of crystallization is abstracted from the salts.