Oxalate ions fluoride

Ethylenediamine tetraacetic acid (EDTA) [60-00-4] (Sequestrene), an anticoagulent at 1 mg of the disodium salt per mL blood, complexes with and removes calcium, Ca ", from the blood. Oxalate, citrate, and fluoride ions form insoluble salts with Ca " and chelate calcium from the blood. Salts containing these anticoagulants include lithium oxalate [553-91-3] 1 mg/mL blood sodium oxalate [62-76-0]2 mg/mL blood ... 

In acidic solution MnOj is usually the end product, although particularly vigorous reductants, e.g. iodide and oxalate ions, convert permanganate to manganous ions. Mn(III) is stable only in acidic solution or in the form of a complex, e.g. with pyrophosphate ion, and it has seldom been reported as the end product of a permanganate oxidation, e.g. for that of Mn(II) in a phosphate buffer and for those of alcohols and ethers in the presence of fluoride ion. ... 

The permanganate oxidation of oxalic acid has been studied exhaustively and has been reviewed by Ladbury and Cullis . It is characterised by an induction period and a sigmoid dependence of rate upon time. Addition of manganous ions eliminates the induction period and produces first-order decay kinetics . Addition of fluoride ions, however, practically eliminates reaction . ... 

A widely applicable masking agent is sodium triphosphate, Na5P3Oi0-6H2O, which readily complexes with a very wide variety of cations in all groups of the Periodic Table, preventing their precipitation by alkali hydroxide, ammonia, phosphate, carbonate or borate. It is used commercially as Calgon to mask calcium which cannot then form precipitates with citrate, fluoride or oxalate ions and in many other instances (see Table 3). 

After separation by ion exchange, the actinides may be precipitated by fluoride or oxalate in macroscopic amounts or collected on an insoluble fluoride precipitate for trace quantities. 

Various fluorides may be precipitated from aqueous solution for use as constituent powders in solid state reactions. Co-precipitation offers very elegant access to intimate mixtures, but the actual products are strongly dependent on the fluoride ion activity within the solution but also on the stability constants of the respective metal complexes. Accordingly, not only anhydrous fluorides are obtained, but also hydrated fluorides or hydroxide fluorides, which may be very difficult to convert to pure fluorides. As noted already [3], reactive compounds, e.g. carbonates, acetates, oxalates, hydroxides etc., which quite easily dissolve in acidic HF solutions, are the preferred starting materials for fluoride syntheses. In contrast, many oxides which have been heated to rather high temperature are frequently unreactive and may not dissolve at all. To enhance reactivity but also improve crystallinity of the product, it has proved useful to perform reactions above the boiling point of water in adapting the hydrothermal method, which has already been shown to be useful in the recrystallisation of materials which are more or less insoluble at ambient temperatures and pressures. Up to about 240°C even PTFE vessels may be used. A number of selected examples with respective reaction conditions are listed in Table 3. 

The activity of the enzyme is also strongly affected by the presence of inhibitors. Fluoride ions inhibit urease (173) and oxalate ions inhibit lactate oxidase (174), but the major inhibitors are heavy-metal ions, such as Ag+, Hg +, Cu " ", organophosphates, and sulfhydryl reagents (/i-chloromercuribenzoate and phenylmercury(II) acetate), which block the free thiol groups of many enzyme active centers, especially oxidase (69). Inhibiting the enzyme electrodes makes it possible to quantify the inhibitors themselves (69), for example, H2S and HCN detection using a cytochrome oxidase immobilized electrode (176). 

Potentiometric detection of anions is feasible when an electrode is available that responds quickly, reversibly and reproducibly to the concentration (or more precisely to the activity) of sample ions. It is often possible to detect a given ion or class of ions with excellent selectivity. For example, solid-state or crystalline ion selective electrodes have been used in IC to detect halide anions. The fluoride ion-selcclivc electrode is particularly selective [20,21]. A copper wire electrode has been used to detect anions such as iodate, bromide and oxalate [22]. 

The general chemistry closely resembles that of the lanthanides. The halides, MX3, may be readily prepared and are easily hydrolyzed to MOX. - The oxides -MjOj, -are known-only for-Ae —Pu and heavier elements. In aqueous solution there are M3+ ions, and insoluble hydrated fluorides and oxalates can be precipitated. Isomorphism of crystalline solids is common. 

Approximately 50% of an absorbed dose is transformed to fluoride ion, dichloroacetic acid, methoxydifluoroacetic acid, and oxalic acid (50). Because of fluoride ion associated renal impairment, the duration of anesthesia using methoxyflurane must be limited (51,52). 

The trivalent actinides such as " Am follow the same precipitation reactions as the trivalent rare earth radionuclides, notably with insoluble hydroxides, fluorides, and oxalates. Numerous solvent extraction and ion-exchange separations from other trivalent radionuclides are reported. Americium radionuclides can be... 

The test is stated to be very selective, but a few interferences are possible. Redox reagents interfere by taking all iron to either oxidation level two or three. Ions that form complexes with iron, e.g., fluoride or oxalates, can ultimately prevent tire prussian blue reaction. ... 

Colored salts like copper, chromium, cobalt, and nickel will reduce the sensitivity of the test, and all heavy metals are expected to interfere. No elements are stated to give a false positive reaction, but a number of ions can interfere. Reductants, like tin(II), can reduce Fe to Fe and will (ultimately) give a false negative result. Ions capable of forming strong complexes with the ions of the test are another cause of interference. Fluoride, acetate, oxalate, and tartrate are examples. 

In the processing of nuclear materials, precipitation/coprecipitation techniques are used for the separation of the actinides from most fission products. Both fluoride and oxalate complexes of these metal ions are sufficiently insoluble to accomplish this separation (Stary 1966). Coprecipitation with bismuth phosphate has also been used for this purpose (Stary 1966). Because of their insensitivity to subtle changes induced by minor cation-radius changes, such techniques are not useful for the separation of the lanthanides from the trivalent actinide metal ions. 

This test is especially useful for the detection of thiocyanate in the presence of large amounts of salts which interfere with the familiar ferric thiocyanate color test by masking ferric ions. Fluorides, phosphates, oxalates, and salts of organic hydroxyacids belong in this category. 

The complex between zirconium and alizarine red S (sodium 3,4-dihydroxy-9,10-dioxo-2-anthracene sulfonate. Figure 6.2) gives red-brown color in acid solution if alizarine red S is in excess and violet color if the zirconium is in excess. The complex is decolorized by fluoride ions. Phosphate, arsenate, sulfate, thiosulfate, and oxalate as well as organic hydroxy acids interfere with this reaction. 

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