Sodium fluoride, complex

Scheme 2.2 After adsorption by solid sodium fluoride complex and sensitive organic compounds can be cleanly perfluorinated [9],...

Fig. 10. The molar refractivity of sodium fluoride complexes of tri-, tetra-, and pentavalent elements versus composition...

Assay of beryUium metal and beryUium compounds is usuaUy accompHshed by titration. The sample is dissolved in sulfuric acid. Solution pH is adjusted to 8.5 using sodium hydroxide. The beryUium hydroxide precipitate is redissolved by addition of excess sodium fluoride. Liberated hydroxide is titrated with sulfuric acid. The beryUium content of the sample is calculated from the titration volume. Standards containing known beryUium concentrations must be analyzed along with the samples, as complexation of beryUium by fluoride is not quantitative. Titration rate and hold times ate critical therefore use of an automatic titrator is recommended. Other fluotide-complexing elements such as aluminum, sUicon, zirconium, hafnium, uranium, thorium, and rate earth elements must be absent, or must be corrected for if present in smaU amounts. Copper-beryUium and nickel—beryUium aUoys can be analyzed by titration if the beryUium is first separated from copper, nickel, and cobalt by ammonium hydroxide precipitation (15,16). 

The trend in architectural applications has been towards more matt finishes, and the sodium hydroxide-based etchants used frequently contain additives such as sodium nitrate or nitrite or sodium fluoride. Chelating agents such as gluconates, heptonates or sorbitol are added to complex the aluminium produced, and other additives such as sulphides may be present in the etchant to complex zinc dissolved from the alloy, and allow it to be used continuously without dumping ... 

L.A. Kamenskaya Phys.-Chem. investigations of interactions between niobium and tantalum complex fluorides and oxyfluorides and potassium and sodium fluorides and chlorides in molten conditions. - Abstracts of Dissertation, Kiev, 1976 (in Russian). 

A mixture of tin(IV) and lead(II) ions may be complexed by adding an excess of standard EDTA solution, the excess EDTA being determined by titration with a standard solution of lead nitrate the total lead-plus-tin content of the solution is thus determined. Sodium fluoride is then added and this displaces the EDTA from the tin(IV)-EDTA complex the liberated EDTA is determined by titration with a standard lead solution. 

Acetylcyclohexanone. Method A. Place a mixture of 24-6 g. of cyclohexanone (regenerated from the bisulphite compound) and 61 g. (47 5 ml.) of A.R. acetic anhydride in a 500 ml. three-necked flask, fitted with an efficient sealed stirrer, a gas inlet tube reaching to within 1-2 cm. of the surface of the liquid combined with a thermometer immersed in the liquid (compare Fig. II, 7, 12, 6), and (in the third neck) a gas outlet tube leading to an alkali or water trap (Fig. II, 8, 1). Immerse the flask in a bath of Dry Ice - acetone, stir the mixture vigorously and pass commercial boron trifluoride (via an empty wash bottle and then through 95 per cent, sulphuric acid) as fast as possible (10-20 minutes) until the mixture, kept at 0-10°, is saturated (copious evolution of white fumes when the outlet tube is disconnected from the trap). Replace the Dry Ice-acetone bath by an ice bath and pass the gas in at a slower rate to ensure maximum absorption. Stir for 3 6 hours whilst allowing the ice bath to attain room temperature slowly. Pour the reaction mixture into a solution of 136 g. of hydrated sodium acetate in 250 ml. of water, reflux for 60 minutes (or until the boron fluoride complexes are hydrolysed), cool in ice and extract with three 50 ml. portions of petroleum ether, b.p. 40-60° (1), wash the combined extracts free of acid with sodium bicarbonate solution, dry over anhydrous calcium sulphate, remove the solvent by... 

Heats of precipitation have been employed to determine the enthalpies of sparingly soluble simple and complex fluorides for example, that of calcium fluoride by adding solid calcium chloride to a solution of excess sodium fluoride saturated with calcium fluoride (88), and of lead chlorofiuoride by adding sodium fluoride solution to a saturated lead chloride solution (50). 

A further spectrophotometric method [3, 4] for water soluble boron in soil, boron is extracted from soil with boiling water. Borate in the extract is converted to fluoroborate by the action of orthophosphoric acid and sodium fluoride. The concentration of fluoroborate is measured spectrophotometrically as the blue complex formed with methylene blue and which is extracted into 1, 2-dichloroethane. Nitrates and nitrites interfere they are removed by reduction with zinc powder and orthophosphoric acid. 

Katz, S. Use of high-surface-area sodium fluoride to prepare MFj. 2 NaF complexes with UFg, WFg, MoFg. Inorg. Chem. 3, 1598 (1964). 

We must, however, ensure that there is no contaminant such as free Fe3+ in the solution before the potassium iodide is added otherwise, more I- will be oxidized than there is Cu2+ in the sample (reaction 15.12). The effective concentration of Fe3+ can be reduced to negligible levels by adding sodium fluoride to complex it. (The divalent copper ion is little affected.)... 

By running a potentiometric precipitation titration, we can determine both the compositions of the precipitate and its solubility product. Various cation- and anion-selective electrodes as well as metal (or metal amalgam) electrodes work as indicator electrodes. For example, Coetzee and Martin [23] determined the solubility products of metal fluorides in AN, using a fluoride ion-selective LaF3 single-crystal membrane electrode. Nakamura et al. [2] also determined the solubility product of sodium fluoride in AN and PC, using a fluoride ion-sensitive polymer membrane electrode, which was prepared by chemically bonding the phthalocyanin cobalt complex to polyacrylamide (PAA). The polymer membrane electrode was durable and responded in Nernstian ways to F and CN in solvents like AN and PC. 

Ethylenediamine tetraacetic acid (EDTA) [60-00-4] (Sequestrene), an anticoagulent at 1 mg of the disodium salt per mT. blood, complexes with and removes calcium, Ca2+, from the blood. Oxalate, citrate, and fluoride ions form insoluble salts with Ca2+ and chelate calcium from the blood. Salts containing these anticoagulants include lithium oxalate [553-91-3] LyC204, 1 mg/mL blood sodium oxalate [62-76-0] Na2C204, 2 mg/mL blood potassium oxalate monohydrate [6487-48-5] H20, 2 mg/mL blood sodium fluoride [7681-49-4] NaF, 2 mg/mL blood trisodium citrate... 

As a result, the electromotive force (EMF) of the cell is zero In the presence of fluoride ions, cerium(IV) forms a complex with fluoride ions that lowers the cerium(IV)-cerium(III) redox potential The inner half-cell is smaller, and so only 5 mL of cerium(IV)-cenum (III) solution is added To the external half-cell, 50 mL of the solution is added, but the EMF of the cell is still zero When 10 mL of the unknown fluoride solution is added to the inner half-cell, 100 mL of distilled water is added to the external half-cell The solution in the external half-cell is mixed thoroughly by turning on the stirrer, and 0 5 M sodium fluoride solution is added from the microburet until the null point is reached The quantity of known fluoride in the titrant will be 10 times the quantity of the unknown fluoride sample, and so the microburet readings must be corrected prior to actual calculations... 

Jaymen et al. [17] and other workers [18-20] found that aluminium in plant digests enhances the iron-1,10-phenanthroline colour, leading to high results in the determination of iron. Both the iron and aluminium complexes of phenanthroline exhibit identical absorption characteristics. Attempts to mask the aluminium in solution with sodium fluoride have been unsuccessful, as the fluoride ions suppress the colour formed with iron and reagent. The determination of iron after the separation of aluminium and phosphates is simple and rapid. This method is reliable and recoveries are quantitative. 

Se(VI), total Se Complexed with 2,3 diaminonapthalene with EDTA-sodium fluoride Spectrofluorometry 0.4ng [292]... 

Many inhibitors of catabolic pathways cause a decrease in cellular heat dissipation. They are therefore valuable tools to indicate the sources of the dissipation and give clues to the relative importance of each pathway in overall metabolic activity (see reviews by Kemp, 1987, 1993 Monti, 1987, 1991). To give a few examples from these reviews, sodium fluoride is a classical inhibitor of glycolysis and it has been shown to substantially reduce heat dissipation by human erythrocytes, lymphocytes, neutrophils, and murine macrophages, indicating the contribution of this pathway to metabolic activity. Cyanide inhibits oxidative phosphorylation by mitochondria at the cytochrome c oxidase complex (site 3) and studies revealed that it decreased heat production in a mouse LS-L929 fibroblast cell line but had no effect on human erythrocytes and neutrophils and murine macrophages, all of which lack mitochondria. Sodium azide inhibits at the same site and so it should come as no surprise that it had no effect on human neutrophils and lymphocytes, but it did reduce heat production by lymphocyte hybridoma cells, which contain... 

The impressive electrolytic systems due to Ziegler and co-workers are perhaps most widely known. These are based on research dating back to 1955. There are several patents on the electrolysis of sodium fluoride-trialkylaluminum complexes with a lead anode 334>, and the electrolysis of sodium or potassium tetraalkylaluminum 336>, as in the following examples ... 

Similar to solution complexation, surface complexation can be distinguished between inner-spherical complexes (e.g. phosphate, fluoride, copper), where the ion is directly bound to the surface, and outer-spherical (e g. sodium, chloride) complexes where the ion is covered by a hydration sleeve with the attraction working only electrostatically. The inner-sphere complex is much stronger and not dependent on electrostatic attraction, i.e. a cation can also be sorbed on a positively charged surface (Drever 1997). 

Add 2 g of sodium fluoride, boil the mixture for 2 to 5 min, and cool in a stream of running water. Titrate the EDTA (which is released by fluoride from its aluminum complex) with 0.01 M Zinc Sulfate to the same transitory yellow-brown or pink endpoint as described above. 

Another method for separating beryllium and aluminium consists of adding excess of a solution of sodium fluoride to the solution. The complex hexafluoro-aluminate, [A1F6]3 , is formed from which the metal is not precipitated as hydroxide by ammonia solution. Beryllium is, however, readily precipitated as the hydroxide under these conditions. 

---