Fluoride determination

Eluorspar assay may be completed by fluoride determination alone, because the mineralogical grouping rarely iacludes fluorine minerals other than fluorite. Calcium can be determined as oxalate or by ion-selective electrodes (67). SiUca can be determined ia the residue from solution ia perchloric acid—boric acid mixture by measuriag the loss ia weight on Aiming off with hydrofluoric acid. Another method for determining siUca ia fluorspar is the ASTM Standard Test Method E463-72. 

EXPERIMENTAL DESIGN APPLIED TO THE OPTIMIZATION OF A DISTILLATION PROCESS FOR FLUORIDE DETERMINATION IN ANHYDRITE... 

This input to design refers to the long-term stability of the raw material sources for the plant. It is only of importance where the raw materials can or do contain impurities which can have profound effects on the corrosivity of the process. Just as the design should cater not only for the norm of operation but for the extremes, so it is pertinent to question the assumptions made about raw material purity. Crude oil (where HjS, mercaptan sulphur and napthenic acid contents determine the corrosivity of the distillation process) and phosphate rock (chloride, silica and fluoride determine the corrosivity of phosphoric acid) are very pertinent examples. Thus, crude-oil units intended to process low-sulphur crudes , and therefore designed on a basis of carbon-steel equipment, experience serious corrosion problems when only higher sulphur crudes are economically available and must be processed. 

After titrating sodium hydroxide with hydrofluoric acid, a chemist determined that the reaction had formed an aqueous solution of 0.020 mol/L sodium fluoride. Determine the pH of the solution. 

J. Marcos, A. Townshend, Fluoride determination by its inhibitory effect on immobilized liver esterase. Anal. Chim. Acta 310 (1995) 173-180. 

Certain precautions are observed in the fluoride determination to deal with contamination problems. The reagents and deionized water used are kept separate and used only for the fluoride analysis. Each new batch of water or reagent is analyzed for fluoride. Finally, the fluoride... 

Baumann, E. W. Trace Fluoride Determination with Specific Ion Electrode. Anal. Chim. Acta 42, 127 (1968). 

Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1 N perchloric acid is equivalent to 20.12 mg of C4H4KNO4S. Fluoride Determine as directed in Method III under Fluoride Limit Test, Appendix IIIB, using a 4-g sample. 

Fluoride Determine as directed in Method V under Fluoride Limit Test, Appendix IIIB. 

Assay Dissolve about 1 g of sample, accurately weighed, in 50 mL of water, add 50.0 mL of 0.05 M disodium EDTA and 20 mL of pH 4.5 buffer solution (77.1 g of ammonium acetate and 57 mL of glacial acetic acid in 1000 mL of aqueous solution), and boil gently for 5 min. Cool, and add 50 mL of alcohol and 2 mL of dithizone TS. Back titrate with 0.05 M zinc sulfate to a bright rose-pink color. Perform a blank determination (see General Provisions), and make any necessary correction. The milliliters of 0.05 M disodium EDTA consumed is equivalent to 50 minus the milliliters of 0.05 M zinc sulfate used. Each milliliter of 0.05 M disodium EDTA is equivalent to 23.72 mg of A1K(S04)2T2H20. Ammonium Salts Add 1 g of sample to 10 mL of 1 N sodium hydroxide in a small beaker, and heat on a steam bath for 1 min. The odor of ammonia is not perceptible. Fluoride Determine as directed in Method V under Fluoride Limit Test, Appendix IIIB. 

Arsenic Determine as directed under Arsenic Limit Test, Appendix IIIB, using a solution of 1 g of sample in 35 mL of water. Fluoride Determine as directed in Method /Funder the Fluoride Limit Test, Appendix IIIB, using a 2-g sample, Buffer Solution B, and 0.1 mL of Fluoride Standard Solution. 

Fluoride Determine as directed under Fluoride Limit Test, Appendix NIB, using 1.0 g of sample, accurately weighed. Lead Determine as directed under Lead Limit Test, Appendix IIIB, using 10 mL of the following solution and 4 pig of lead (Pb) ion in the control Transfer 4.0 g of sample, accurately weighed, into a 250-mL beaker, cautiously add 50 mL of nitric acid, and evaporate just to dryness on a steam bath. Add 20 mL of nitric acid, repeat the evaporation, cool, and dissolve the residue in sufficient water containing 4 drops of nitric acid to make 40.0 mL. 

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