07 September 1984
Vol 225, Issue 4666

About The Cover

Photomicrograph showing a cross section of a water-swollen polyvinyl alcohol film (thickness, 0.18 millimeter) containing silver bromide precipitate. The precipitate was formed by immersing a 10-cubic-centimeter polyvinyl alcohol pouch containing 0.05M silver nitrate in 100 cubic centimeters of 0.05M sodium bromide for 16 hours. Silver nitrate-contacting side is up. The photograph was taken in polarized light with crossed (right) and uncrossed (left) polarizers. See page 1021. [K. F. Mueller, CIBA-GEIGY Corporation, Ardsley, New York 10502]