Positive and Negative Ions from Molten Silicates Coated on Platinum-Rhodium Filament

Abstract

Positive and negative ions from some molten silicates coated on a Pt-Rh (10%) filament have been measured using mainly a Hitachi RM-6E single-focusing mass spectrometer. The samples used are Li₂O-SiO₂ (mole ratio 2: 1 and 3: 1), Na2O-Si02 (1: 1 and 2: 1), K₂O-Si0₂ (1: 1), Cs₂0-Si0₂ (1: 1), PbO-Si0₂ (2: 1), Li₂0-Pb0-Si0₂ (2: 1: 1 and 1: 1: 2), and K₂O-PbO-Si0₂ (2: 1: 3). The temperatures of samples are read with an optical pyrometer, but the readings can not be corrected for emissivity and window transmission. The apparent temperaturerange is between 800°C and 1 400°C.
The negative ions O^-, O₂^-, SiO₃^-, MSi0₃^- (M=Li, K, and Cs), Rh0₂^-, RhO^-₃, and Pt0₂^- are found for all the systems investigated, except Pb0-Si0₂ (2: 1) and Li₂O-Pb0-Si0₂ (1: 1: 2). The proportions of these ions from K₂O-PbO-Si0₂ and K₂0-Si0₂ are particularly large compared with those from the other systems.
When PbO is added to a K₂0-Si0₂ system, the lowest temperature at which the negative ions are detected is lowered. The intensities of these ions are also increased by the addition of PbO.
The positive ions M⁺, M₂⁺, M₂0⁺ (M =Li, Na, K, and Cs), 0, ⁺ 0₂⁺, and Si⁺ are obtained from all systems, except PbO-SiO₂ (2: 1). The ions Li₃O⁺ and Li₃SiO₃⁺ are found in the mass spectra of Li₂0-Si0₂ and Li₂O-PbO-Si0₂. The ions containing Pb, such as LiPb0⁺, are found in the mass spectra of Li₂O-Pb0-Si0₂.