fototropica lens with a refractive index greater than or equal to one and 59.a number of abbe greater than or equal to 44 and a density of less than or equal to three grams per cubic centimeter

摘要

a phototropes glass with optical position n d 1.59 and v (d) 44 and a density of 3.0 g cm 3 is first described.the composition of the grundglases lies in the system sio 2 - r 2o 3 r 2o ro ro x - r 2o 5, with preference for al 2o 3 r 2o 3 and b 2o 3, r 20 for alkalimetalloxide, ro for erdalkalimetalloxide and zno, ro x for their own measurements, 2 and tio 2 and r 2o 5 nb 2o 5, and with silver oxide, copper oxide and halogens to produce the phototropie are included.