Abstract: A method of protecting a metal against embrittlement when the metal is exposed to carbon or sulfur at an elevated temperature, the method comprising forming a thin, adherent, continuous coating of a glass on the surface of the metal prior to exposure to carbon or sulfur at an elevated temperature.

Abstract: A silver halide photochromic glass hasa. a clear luminous transmittance of about 90%,b. A darkened luminous transmittance at 20.degree. C. below about 25%.c. A fading rate at 20.degree. C. such that, after a five minute fading interval, the glass exhibits a percent faded luminous transmittance that is no more than the darkened luminous transmittance percentage plus 15. The glass has an R.sub.2 O--Al.sub.2 O.sub.3 --B.sub.2 O.sub.3 --SiO.sub.2 base composition, contains as additives, in percent by weight, 0.1-0.3% Ag, 0.25-1.0% Cl, 0-0.2% Br, 0.25-1.0% Cl+Br, the ratio of Ag:(Cl+Br) being 0.15-0.65, 0.003-0.015% CuO and 0.1-1.0% PbO and the total R.sub.2 O content is 8-13.5%, wherein R.sub.2 O consists of Li.sub.2 O+Na.sub.2 O +K.sub.2 O.

Abstract: This invention is concerned with glass-ceramic articles having compositions within a very narrowly-delimited area of the MgO-Al.sub.2 O.sub.3 -B.sub.2 O.sub.3 -SiO.sub.2 field and having alpha-quartz and sapphirine as the principal crystal phases, resulting from nucleation through a combination of TiO.sub.2 and ZrO.sub.2. Upon contacting such articles with lithium ions at an elevated temperature, said lithium ions will replace magnesium ions on a two Li.sup.+-for-one Mg.sup..sup.+2 basis within the crystal structures, thereby providing a unitary glass-ceramic article having an integral surface layer wherein the principal crystal phase is a lithium-stuffed beta-quartz solid solution. That transformation of crystal phases results in compressive stresses being set up within the surface layer as the articles are cooled.