The Colours of Nickel in Glasses of Various Types and their Implications Concerning Glass Structure. Part III. Studies of the Absorption Spectra of Nickel in Various Solutions and in Certain Organic Compounds, also of the Magnetic Properties of Nickel in the Various Experimental Glasses, in Relation to the State of Nickel in the Different Glasses

JSGT 1955 V39 T287-T313

To obtain further information relating to the states in which nickel can exist in glass, the absorption spectra of nickel salts and solutions, and of certain complex compounds, have been investigated, also the magnetic properties of nickel in the various experimental glasses. The conclusions drawn from the experimental observations carried out during the whole of the investigations are: (1) Nickel as a divalent ion in the simplest possible co-ordination with oxygen gives the "brown" type of transmission curve; this would correspond with the Ni⁺ ion occupying a position between two O^- ions single-bonded to structure-building units, i.e. in a "bridging" position between structure-building units. (2) Nickel as a divalent ion in 6-fold co-ordination within the interstices of the glass structure gives the" green" type of curve. (3) The "undulatory" form of curve is attributed to nickel as a divalent ion associated with the alkali ions and with oxygen ions in complex systems of the form Ni(OLi)₄^2-, Ni(ONa)₄^2-, etc. These are most probably tetrahedral in form, with the nickel ion at the centre, the oxygens at the corners and the alkali ions at the centres or just outside the centres of the faces of the tetrahedra. These complex systems enter the glass structure in "bridging" positions, with two of the oxygen atoms forming corners of the adjoining structure-building units. This group can be resolved into a nickel-ion "bridge" between the two structure-building units, with the alkali ions associated with four other SiO₄ tetrahedra in the immediate neighbourhood. The two alternative configurations would form a "resonance" system in which the resonance point depends on the relative polarising effects of the nickel and the alkali ions on the electron system of the four oxygen ions or atoms associated with them.

H. Moore & H. Winkelmann