Photographic glass is over 22, but docs not do otherwise; and this itself is not alone responsible for more than 2,000 years a (Radon) ae I : ; ; ; ; COCh | 1915 8 I :100,000 1:50,000 BEG Trichlormethyl chloroformate . | 5,554,334 1,637,816 6,002,987 1,512,754 1925 .