Glasses Containing Chrome Oxide, I

Abstract

Glass composed of 72% SiO₂, 12 CaO, and 16R′₂O has been taken as base glass, various studies have been made of glasses by replacing therein their CaO contents with Cr₂O₃ one after another. Chromium oxide used for a coloring agent has been Cr₂O₃. In base glasses whose R′₂O is respectively Na₂O and K₂O if Cr₂O₃ content is respectively about 4% and more than 1% both glasses formed contain more insoluble black chromium oxide and have been found difficult to make them having uniform quality. When R′₂O is Li₂O and the amount of Cr₂O₃ is over 4% a green aventurine glass is obtained, when the like amount is 8% it becomes considerably difficult to be melted and when it is as much as 10% it becomes still more harder and substantially no vitreous state is resulted. Colors of glasses are in all cases green but potash glass is slightly yellowish. Next, sample glasses have been made into plates, polishing their both surfaces and measurements have been made for their transmission of various wave lengths in ultraviolet, vissible and infrared ranges. Judging from the form of transmission curve within vissible range there has been found that the position and grade of selective absorption are somewhat different according to kinds of alkali.