The reaction of simulated rain with copper, copper patina, and some copper compounds.

Simulated rain samples of varying acidities related to precipitation in the New York City metropolitan area environment for the epochs 1890, 1950, and 1980, as well as two additional variants, were used to study accelerated reactions with copper, patinated copper specimens, and thirteen copper compounds (minerals). Cuprite (cuprous oxide) and brochantite (a basic cupric sulfate) formed rapidly under a wide range of conditions. Posnjakite, a hydrated basic cupric sulfate identified in a companion study as a significant early patina component, forms under more limited conditions, sometimes simultaneously with brochantite, but subsequently converts to brochantite.