Fluorine 207 using thorium nitrate

Willard, H. H. and Winter, O. B. (1953). Volumetric method for determination of fluorine using thorium nitrate. Industr. Engng Chem. (Anal, ed.), 5, 7. 

For many years fluorine has been deterrnined by the Willard-Winters method in which finely ground ore, after removal of organic matter, is distilled with 72% perchloric acid in glass apparatus. The distillate, a dilute solution of fluorosiUcic acid, is made alkaline to release fluoride ion, adjusted with monochloroacetic acid at pH 3.4, and titrated with thorium nitrate, using sodium a1i2arine sulfonate as indicator. 

Bomb fusion with alkali has been applied66 to the determination of fluorine in organofluorosilicon compounds. It is recommended that the-large amount of alkali present after the decomposition of the organofluoro compound is removed by the use of a cationite. The test solution followed by water is passed through a column of SDV-3 ion-exchange resin and the combined solution is titrated with standard thorium nitrate solution, using Alizarin red S indicator. 

There are several methods available to determine the amount of carbon-bonded fluorine. One of the earlier methods employed the Schoniger Combustion technique followed by thorium nitrate or cerous chloride titration using sodium alizarin sulfonate or murexide as the indicator (21). 

To analyze the product for phosphorus and fluorine, the latter is first distilled as hexafluosilicic acid in the presence of perchloric acid. The fluorine content of the distillate is then determined by titrating with standard thorium nitrate solution at a pH of about 3, using sodium alizarinsulfonate as the indicator, The phosphorus may be determined in the residue remaining after distillation by precipitating ammonium 12-molybdophosphate, dissolving the precipitate in an excess of standard sodium hydroxide, and titrating the excess base with standard acid. AtuU. Calcd. for NajPOjF F, 13.19 P, 21.53. Found F, 13.17 P, 21.53. 

Quantitative determination of the halogens can be accomplished by a number of procedures. Accurate analysis of fluorine is the most difficult, and is generally carried out either by (1) calcium fluoride precipitation, (2) lead chlo-rofluoride precipitation, or (3) titration with thorium nitrate using sodium alizarin sulfonate as an indicator Th(N03)4(aq) - - 4KF(aq) ThF4(s) - - 4KN03(aq). 

Analysis. Krypton and fluorine, subjected to an electric discharge at about 90 K and 30 torr, react to form a white solid. The solid hydrolyzes with the formation of HF and Kr 0.0380 mg of Kr is recovered, and the titration of the fluoride in solution (with thorium nitrate alizarin sulfonate is used as the indicator) shows the presence of 9.10 X 10 mmole F . What is the empirical formula of the krypton fluoride ... 

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