Radiometric Determination of Inorganic Fluoride

Abstract

Sodium fluoride and sodium hexafluosilicate are titrated with samarium ion containing europium carrier-tracer.The end point is determined by measuring the excess of titrant by a radiometric procedure. Under optimum conditions, 20 to 30 mg. of fluoride can he determined with an error of less than 1%• Dilution of the fluoride by a factor of 5 results in an error generally less than 3%. Errors in the determination of sodium hexafluosilicate are greater than with sodium fluoride.Colloid flocculation is usually incomplete. The colloid remaining in suspension leads to low results.Acetic acid helps considerably in flocculating the colloid, but many other flocculents cause coprecipitation and high results. The titration can also be done on a micro scale. Fluoride in the amount of 38 7 is determined with generally less than 2% error.

Principles of Isotope Dilution Assays

“…If this approach is to be successful, the stoichiometry of the reaction contemplated must be known, and reliable methods must be available for removing excess reagent and for separating the desired derivative from incidental labeled products. If quantitative recovery of the product is possible, as appears to be true in certain cases, the radioactivity of the derivative, B c.p.m., permits calculation of the number of millimoles involved from the expression X = ~~= ^millimole So A This approach, which requires no weighing or other assay procedures, appears to have been applied successfully to certain amino acids (6, 32, S3, 65), to sulfate in plating baths (17) by precipitation with radioactive barium, and to the microdetermination of iodide (42), iodate, and a number of other inorganic ions (28,36,39,57). This procedure has been referred to as radiometric analysis (20).…”

Air Pollution

“…Other papers among many on this subject have involved fluorometry (347,480), cathode ray polarography (287), spectrophotometry (193,195 , 273), a study of colorimetry of organoferric complexes bleached by low concentration of fluorides (318), electrochemistry (25), ion exchange resins (319), and isotopes (324) Organic Fraction of Air-Borne Particulates.…”

Novel Radiotracer Method for Fluoride Determination.

“…Essentially all current methods for fluoride are of the negative type; that is, the fluoride ion bleaches a metal dye indicator, and the decrease in color is measured colorimetrically. Similarly, previous methods using radiotracers (4,6) have depended on measuring the decrease in radioactivity after a particular reaction. Recently a positive colorimetric method for fluoride ion has been developed by Belcher, Leonard, and West (1).…”