Chlorine, determination fluoride

Chlorine and fluorine in beryUium metal are isolated by pyrohydrolysis or by distUlation (21). Fluoride and chloride in the condensate are determined by ion-selective electrode or colorimetricaUy. 

Discussion. This method is based upon the precipitation of lead chlorofluoride, in which the chlorine is determined by Volhard s method, and from this result the fluorine content can be calculated. The advantages of the method are, the precipitate is granular, settles readily, and is easily filtered the factor for conversion to fluorine is low the procedure is carried out at pH 3.6-5.6, so that substances which might be co-predpitated, such as phosphates, sulphates, chromates, and carbonates, do not interfere. Aluminium must be entirely absent, since even very small quantities cause low results a similar effect is produced by boron ( >0.05 g), ammonium (>0.5 g), and sodium or potassium ( > 10g) in the presence of about 0.1 g of fluoride. Iron must be removed, but zinc is without effect. Silica does not vitiate the method, but causes difficulties in filtration. 

Chlorine fluoride, 21 235, 236, 238, 240, 242, 244, 246, 247, 249 geometry of, 18 320-322 oxygenation of, 18 349 oxygen-containing, 21 245 Chlorine fluoride oxide radicals, 18 385, 386 Chlorine hydroxide, 5 219 Chlorine isotope, half-life determination, 2 ... 

Dienstbach and Bachmann [38] have determined plutonium in amounts down to 20 fCiP/ug soil in sandy soils by an automated method based on gas chromatographic separation and a-spectrometry. In this procedure, the sample is decomposed completely by hydrogen fluoride. The hydrogen fluoride is evaporated and the residue is chlorinated. Plutonium is separated from the sample by volatilisation and separation of the chlorides in the gas phase. The plutonium is deposited on a glass disk by condensation of volatilised plutonium chloride. The concentration of plutonium is then determined by a spectroscopy. 

Spectrophotometric techniques based on molecular absorption radiation for determining nutrients (NO3, N02, NII4, N2, phosphorus, and silicon) as well as chlorine, fluoride, cyanide, sulfate, and sulfide. 

Table 12.6 sets out other standard methods for the determination of nonmetallic substances chloride is determined by titration,50 51 73 VIS spectrophotometry,50 74 and ISE 51 chlorine by titration and VIS spectrophotometry 75-77 fluoride by VIS spectrophotometry50 and ISE 50 78 79 iodide by VIS spec-trophotomtery 50 cyanide by titration, VIS spectrophotometry, and ISE 50 80 81 sulfate by gravimetry50 51 and turbidimetry 50 sulfite by titration and VIS spectrophotometry 51 and sulfur by titration and VIS spectrophotometry.50 51... 

The 5-position in 1,2,4-thiadiazoles is most reactive in nucleophilic substitution reactions. Chlorine, for example, may be displaced by nucleophiles (Nu) such as fluoride, hydroxide, thiol, amino, hydrazino, sulfite and azido groups (Scheme 11). Active methylene compounds such as malonic, acetoacetic and cyanoactic esters as their sodio derivatives also displace the 5-halo substituent (65AHC(5)ll9). The reaction follows second-order kinetics, the rate determining step being addition of the nucleophile at C-5 followed by rapid elimination of X. 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

The analysis of chlorine trifluoride has been routinely performed by a gas chromatographic technique using a specifically designed corrosion resistant instrument. Well-defined chromatographic peaks are obtained for chlorine trifluoride and all normally expected components, except hydrogen fluoride. The hydrogen fluoride content is determined by an independent near infrared method. 

The reaction stoichiometries, product profiles, and apparent second-order rate constants for the combination of perfluoroaromatic molecules (and several hydro and dihydro derivatives) with excess superoxide ion in dimethylformamide are summarized in Table 7-1. The primary product from the combination of C6F6 with 2 equivalents of O2-- is CeEgOO on the basis of the F-NMR spectrum of the product solution and the mass spectrum for the major peak from the capillary GC of the product solution.24 Similar analyses of the product solutions for the other fluoro substrates are consistent with a peroxide product from the displacement of a fluoride ion. A reasonable first step for these oxygenations is nucleophilic addition of O2 - to the polyfluoroaromatic. Subsequent loss of fluoride ion will give an aryl peroxy radical, which will be reduced by a second O2-- to the aryl peroxide product. This reaction sequence (with the initial nucleophilic displacement the rate-determining step) is analogous to that observed for chlorohydrocarbons and polychlorobenzenes (Scheme 7-8). However, the peroxo product of the latter systems is an effective nucleophile that attacks a second substrate molecule (or an adjacent aryl chlorine... 

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