The Indirect Determination of Fluorine in Coating of Low Hydrogen Type of Arc Welding Electrode and Its Raw Materials by Separating Precipitated CeF₃ and Flame Emission Spectrometry

Abstract

An indirect determination of F by flame emission spectrometry was studied. After a sample was fused with Na₂CO₃, F was precipitated as CeF₃, and Ce in CeF₃ which was separated by filtering was determined by flame emission spectrometry in a nitrous oxide-acetylene flame.
The intensity of Ce in the concentration range of 0 to 1 200 ppm was measured at 520nm, and was increased by adding Sr.
When the minimum of CH₃COONH₄ which was necessary to precipitate CeF₃ rapidly was added to the solution, co-precipitated cerous acetate could be dissolved by washing with NH₄NO₃ solution when filtering the precipitate.
The recovery of 5 mg or over F was 98-102%.
This method was successfully applied to the determination of F in the coating of the low hydrogen type of electrode, fluorides of alkaline earth metals, and cryolite. The reproducibility (coefficient of variation) of the results was 1.46-3.48%.