Color of glass

Thus, most of the color in glass is produced by metallic ions derived from minerals, usually in relatively small amounts within the glass structure. Already in antiquity there was awareness of the effects of some other metals on the color of glass. It was known then, for example, that even relatively small amounts of specific metals, included as minerals in the components of a glass melt, could produce colored glass particular metalliferous minerals were therefore added to glass melts so as to produce special and... 

In 1899, the Curies first reported the coloration of glass and porcelain and the formation of ozone from oxygen by radioactive radiation. Giesel (1900) noted that the coloration of alkali halides under these radiations was similar to the effect of cathode rays he also observed the decomposition of water. R Curie and Debierne (1901) observed continuous evolution of hydrogen and oxygen... 

Triarylmethane dyes can be used for the coloration of glass. Other high technology applications using triarylmethane dyes include electrophotog-laphy and optical data stoiage. 

The addition of many other substances to sand, soda, and lime produces specialty glasses having different colors. Some of the materials that can be added and the colors of glasses that result are as follows ... 

Table 2.7. Colors of Glass Resulting From Doping...

The coloration of glass is achieved by the addition of inorganic metal compounds to the molten glass. The metal ions responsible for the colors of various glasses are presented in Table 2 (17). 

Coloration of glasses by 3d transition metals ions is due to electronic transitions between normally degenerate energy levels of d-electrons. Since a detailed description of the mechanism leading to these electronic transitions (called ligand field or crystal field theory) can be found in many places, only a brief qualitative discussion will be provide here. 

Since the coloration of glasses by transition metal and rare earth ions results from ligand field effects, several general trends can be predicted. First, a change in oxidation state results in a change in the number of 3d or 4f electrons, resulting in a different number of possible electronic transitions for otherwise identical conditions. Since each possible electronic transition represents an absorption with a different energy, a difference in oxidation state will result in a different absorption spectrum. 

Details of the coloration of glasses due to ligand field effects are further complicated by the possibility of redox interactions between two or more different transition metal ions. Other elements such as arsenic and antimony, which do not directly affect color, may alter the oxidation state of a coloring ion and alter the color of the glass. Changes in furnace atmosphere can also inadvertently alter the oxidation state of coloring ions due to changes in the concentrations of O2, CO, CO2, and H2O vapor. 

Explain why the color of glasses containing Co " will change systematically when F, Cl, Br, or I are added to the melt. 

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