Fluorides traces

Ion-selective electrodes for fluoride trace analysis are commercially available and effective down to a level of mg dm [56]. A recent textbook by Cattrall [57] gives background information to the theory... 

Fluorination and Sorption of Technetium on Magnesium Fluoride Trace quantities of technetium will accompany the... 

Pine needles Apple leaves Peach leaves Spinach leaves Tomato leaves Vegetation Sargasso seaweed SRM 1575 SRM 1515 SRM 1547 SRM 1570a SRM 1573a SRM 2695 NIES-9 M M 11 t1 M M H t M fluoride trace elements n II II II II II NIES II II II 49... 

Antimony Pentachloride 50 160 71 — E - S carbon tetrachloride and refrigerants 42%. hydrogen chloride 8%. hydrogen fluoride trace, slight aeration. 

Alkylated gasoline is a high-quality product from oil industry. The alkylate contains no olefins or aromatics but consists exclusively of isoalkanes. It has a low vapor pressure and a high octane number. In several time this gasoline contains fluoride traces due to inefficient... 

Fluorine occurs widely in nature as insoluble fluorides. Calcium fluoride occurs as jluospar or fluorite, for example in Derbyshire where it is coloured blue and called bluejohn . Other important minerals are cryolite NajAlFg (p. 141) and Jluorapatite CaFjSCaj (P04)2. Bones and teeth contain fluorides and some natural water contains traces. 

Nonmeta.ls, Sulfur reacts with fluorine to yield the remarkably stable sulfur hexafluoride, SF. Operating conditions must be controlled because a mixture of the lower fluorides such as disulfur difluoride [13709-35-8] 2 2 disulfur decafluoride [5714-22-7] 2 10 sulfur tetrafluoride [7783-60-0] SF4, may also be formed. When this reaction is carried out between 310 and 340°C, SF is primarily obtained and essentially no SF and only trace amounts of lower fluorides. Below 300°C, and preferably at ca 275°C, SF is the primary product. At 450—500°C, a mixture comprising ca 50% SF and the lower sulfur fluorides is formed (see Fluorine compounds, inorganic-sulfur). 

Hafnium is readily soluble in hydrofluoric acid and is slowly attacked by concentrated sulfuric acid. Hafnium is unaffected by nitric acid in all concentrations. It is resistant to dilute solutions of hydrochloric acid and sulfuric acid. Hafnium is attacked by all mineral acids if traces of fluorides are present. Hafnium is very resistant to attack by alkaUes. 

Niobic Acid. Niobic acid, Nb20 XH2O, includes all hydrated forms of niobium pentoxide, where the degree of hydration depends on the method of preparation, age, etc. It is a white insoluble precipitate formed by acid hydrolysis of niobates that are prepared by alkaH pyrosulfate, carbonate, or hydroxide fusion base hydrolysis of niobium fluoride solutions or aqueous hydrolysis of chlorides or bromides. When it is formed in the presence of tannin, a volurninous red complex forms. Freshly precipitated niobic acid usually is coUoidal and is peptized by water washing, thus it is difficult to free from traces of electrolyte. Its properties vary with age and reactivity is noticeably diminished on standing for even a few days. It is soluble in concentrated hydrochloric and sulfuric acids but is reprecipitated on dilution and boiling and can be complexed when it is freshly made with oxaHc or tartaric acid. It is soluble in hydrofluoric acid of any concentration. 

Isopiestic or isothermal distillation. This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace metal studies. The procedure involves placing two beakers, one of distilled water and the other of a solution of the material to be purified, in a desiccator. The desiccator is sealed and left to stand at room temperature for several days. The volatile components distribute themselves between the two beakers whereas the non-volatile contaminants remain in the original beaker. This technique has afforded metal-free pure solutions of ammonia, hydrochloric acid and hydrogen fluoride. 

Aluminium fluoride (anhydrous) [7784-18-4] M 84.0, m 250°. Technical material may contain up to 15% alumina, with minor impurities such as aluminium sulfate, cryolite, silica and iron oxide. Reagent grade AIF3 (hydrated) contains only traces of impurities but its water content is very variable (may be up to 40%). It can be dried by calcining at 600-800° in a stream of dry air (some hydrolysis occurs), followed by vacuum distn at low pressure in a graphite system, heated to approximately 925° (condenser at 900°) [Henry and Dreisbach J Am Chem Soc 81 5274 1959]. 

Pretreatment of the collected particulate matter may be required for chemical analysis. Pretreatment generally involves extraction of the particulate matter into a liquid. The solution may be further treated to transform the material into a form suitable for analysis. Trace metals may be determined by atomic absorption spectroscopy (AA), emission spectroscopy, polarogra-phy, and anodic stripping voltammetry. Analysis of anions is possible by colorimetric techniques and ion chromatography. Sulfate (S04 ), sulfite (SO-, ), nitrate (NO3 ), chloride Cl ), and fluoride (F ) may be determined by ion chromatography (15). 

The polymers were first described by Newkirk. Polymerisation may be brought about by subjecting acetylene-free vinyl fluoride to pressures to up to 1000 atm at 80°C in the presence of water and a trace of benzoyl peroxide. 

A reagent which is primarily of interest as a means of converting alcohols into fluorides has been used to dehydrate C-11 alcohols in high yields. 1 la-Alcohols dehydrate rapidly with 2-chloro-l-diethylamino-l,l,2-trifluoro-ethane reagent at low temperature, while 11 j5-alcohols require refluxing methylene chloride. Traces of fluoro compounds have been detected in the products. 

Lithium silylamides react smoothly with tiifluoronitrosomethane to give diazenes Traces ot water initiate the decomposition of the latter with liberation of a trifluoromethyl carbanion, which is trapped by carbonyl compounds [775] (equation 116) Desilylation of trialkyl(trifluoromethyl)silanes by fluoride ion produces also a trifluoromethyl carbanion, which adds to carbonyl carbon atoms [136, 137] (equations 117 and 118)... 

Dissolved mineral salts The principal ions found in water are calcium, magnesium, sodium, bicarbonate, sulphate, chloride and nitrate. A few parts per million of iron or manganese may sometimes be present and there may be traces of potassium salts, whose behaviour is very similar to that of sodium salts. From the corrosion point of view the small quantities of other acid radicals present, e.g. nitrite, phosphate, iodide, bromide and fluoride, have little significance. Larger concentrations of some of these ions, notably nitrite and phosphate, may act as corrosion inhibitors, but the small quantities present in natural waters will have little effect. Some of the minor constituents have other beneficial or harmful effects, e.g. there is an optimum concentration of fluoride for control of dental caries and very low iodide or high nitrate concentrations are objectionable on medical grounds. 

F rom 5-deoxy-5-iodo-1,2-0-isopropylidene-/ -l-arabinofura-nose (37). Anhydrous silver fluoride (600 mg.) was added to a solution of 300 mg. of 37 in pyridine (4.0 ml.), and the mixture was shaken at room temperature for 24 hours. Ether (4 ml.) was added, and the mixture was passed through a column of silica gel (1.5 X 12 cm.). The column was washed with ether/pyridine, 1 1 v/v. (10 ml.), and the effluent, which contained 5-deoxy-l,2-0-isopropylidene-/ -L-threo-pent-4-enofuranose (33), was concentrated to 4 ml. Acetic anhydride (0.2 ml.) was added, and the reaction mixture was kept at room temperature for 16 hours. Concentration afforded a sirup from which the last traces of solvent were removed by storage in high vacuum at 20°C. The sirup was distilled at 90°C. (bath) at 2.5 X HHmm. The distillate (110 mg., 51%), which crystallized on standing, had physical constants which were identical to material prepared as above. 

Ref 5) CA Registry No 1493-05-6 It has been prepd by the reaction of Agnitrite with difluoroiodomethane (Ref 2) by the decarboxylation of difluoronitroacetic acid with anhyd K fluoride (Ref 3), or anhyd K carbonate, yield 46% (Ref 5) or by heating 1,1-difluoro-4-me thyl-1 -ni tro-2-triflu orome thy l-4-penten-2- ol to 100° with a trace of K hydroxide, yield 82% (Ref 4),... 

Horton (H9, H10) has obtained additional acoustic-admittance data for a series of composite propellants. At a given frequency, decreasing the mean oxidizer particle size increases the acoustic admittance and thereby the tendency for instability. Horton also investigated the effects on the acoustic admittance of the incorporation of traces of copper chromite, a known catalyst, for the decomposition of ammonium perchlorate, lithium fluoride (a burning-rate depressant), and changes in binder these data are difficult to analyze because of experimental errors. 

Whereas aryl Grignard compounds afford good yields of sulfones with sulfonyl fluorides298 299, phenyllithium is mainly chlorinated by a-toluene-sulfonyl chloride on the other hand, the corresponding fluoride yields only a trace of the expected mono-sulfonylation product, while the main product is 26 obtained by twofold sulfonylation300 (equation 61). 

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