Aluminium, complex fluorides

Akitt, J. W., Greenwood, N. N. Lester, G. D. (1971). Nuclear magnetic resonance and Raman studies of aluminium complexes formed in aqueous solutions of aluminium salts containing phosphoric acid and fluoride ions. Journal of the Chemical Society, A, 2450-7. 

Since hydrogen ions are six to twelve times more mobile than other cations, there will be a delay between loss of hydrogen ions from solution and migration of glass cations into the aqueous phase. Presumably, this electrical imbalance results in an electric field which acts as a driving force for the migration of cations. Aluminium and fluoride are almost certainly transported as cationic aluminofluoride complexes, AIF and AIFJ, mentioned above. 

Whether mixtures of the perchlorate with aluminium truly detonate is under debate. However, appropriate compositions certainly explode violently even when uncontained, so the deflagration/detonation dispute is essentially academic [1]. Presence of aluminium fluoride increases the ease of ignition of aluminium-perchlorate mixtures, owing to complex fluoride formation [2],... 

Two processes have been proposed to explain the mitogenic effect of fluoride on bone cells involving either fluoride ions directly or the AIF complex (Fig. 11). Fluoride ions have been shown to directly inhibit an enzyme (tyrosine phophory-lase phosphatase) resulting in an enhancement of the tyrosine phosphorylation part of the mitogen-activated protein kinase system (MARK) [177], The other activation pathway involves a complex of aluminium and fluoride which activates the G-protein and stimulates tyrosine phophorylation resulting in an enhanced mitogenic effect [176]. 

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. 

Alva, A.K., Sumner, M.E., Li, Y.C. and Niller, W.P. (1989) Evaluation of three aluminium assay techniques for excluding aluminium complexed with fluoride or sulfate. Soil Sci. Soc. Am.J., 53, 38-44. 

The corresponding chloride and bromide are made by heating the dioxide with carbon tetrachloride and aluminium bromide respectively. The only tetrahalide of plutonium yet isolated is the fluoride, PUF4, although the tetrachloride appears to exist in solution. Americium forms a tetrafluoride and also a complex fluoride, KAmFg. 

A number of metals [including Be, Ga, In, Sc, Fe(III), U, V, and Zr] interfere with the determination of Al. Anions that form complexes with A1 (e.g., fluoride, phosphate, citrate) prevent the formation of the ternary aluminium complex. Before the determination, Al should be separated from interfering elements, or they should be masked. 

In indirect methods for determination of fluoride, aluminium complexes with Eriochrome Cyanine R (ECR) [58] and Xylenol Orange [59] have been applied. The sensitivity of the ECR method increases considerably in the presence of CP [60]. The complexes of scandium with Methylthymol Blue (e = 1.07-10 at 590 nm) and Pyrocateehol Violet [61] have also been recommended. 

The Th complexes with organic reagents have been applied in determinations of fluoride in waters [57] and in organic compounds [4,56]. The Alizarin S method has been automated [55]. The aluminium complex with Xylenol Orange has been used for determining fluorine in phosphates [59]. Fluorine was determined in dental preparations with the use of methylsalicylic acid [43]. 

An alternative fluoride breakdown process for beryl was used during the 1939-45 war by the Sappi Company in Italy. This was based upon the reaction with sodium hydrogen fluoride (NaF.HF) at a temperature of about 680°C. The fluoride reagent is mixed with the ground ore and made into briquettes with a little water, ready for firing in the breakdown furnace. The reaction converts the beryllium to a complex fluoride, believed to be 3NaF.2Bep2, without fluorination of the aluminium and silicon components. 

For multicomponent glasses the reaction mechanism are much more complex. Additional alkali fluorides, alkali earth fluorides, aluminium alkali fluorides and other compounds arise having very different dissolution rates during the reaction (6.3) shows an example. 

The anodic oxidation of magnesium does not normally produce a film that has sufficient corrosion resistance to withstand exposure without further protection by painting, and the solutions used are complex mixtures containing phosphates, fluorides and chromates. In the case of aluminium, a relatively simple treatment produces a hard, compact, strongly adherent film of oxide, which affords considerably increased protection against corrosive attack . 

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 ... 

Fluoride forms a tetrahedral ion with aluminium, ABF , which forms a complex with the GDPXaffy form of G-proteins. In the case of Gs, the complex ABF4CGDP behaves much as GTP or the more stable GTP derivatives, GTPys or GPP(NH)p, and causes activation of adenylyl cyclase through the complex AIF4-XGDPXasXC. 

Bigay, J., Deterre, P., Pfister, C., Chabre, M. (1987). Fluoride complexes of aluminium or beryllium act on G-proteins as reversibly bound analogues of the y-phosphate of GTP. EMBO J. 6, 2907-2912. 

In this system there is a useful cooperative effect between aliuninium, fluoride and calcium, which has been demonstrated by the solution studies of Ellis Wilson (1987). In the absence of aluminium, calcium precipitates as the fluoride at all pHs. Aluminium has the effect of preventing the precipitation of calcium as fluoride, again because it forms strong soluble complexes with fluoride. 

Connick, R. E. Poulsen, R. E. (1957). Nuclear magnetic resonance studies of aluminium fluoride complexes. Journal of the American Chemical Society, 79, 5153-7. 

The most important cation is aluminium. In the absence of fluoride, aluminium is present in solution as the Al(H20)e complex which hydrolyses to form complex multinuclear species such as [Al2(OH)2] and [A1i304(0H)24(H20)i2] + (Avcston, 1965 Waters Henty, 1977). There are also two kinds of phosphate complexes (Akitt, Greenwood Lester, 1971 O Neill et al., 1982) those based on the H3PO4 ligand, A1(H3P04) +... 

The first result in Table 2.2 is the value found directly. The next set of three results shows that recovery of fluoride after deliberate addition to the spiked samples is excellent. The fifth result is that obtained from an acidified sample. The sixth, seventh, eighth, and ninth sets of data show that the expected fluoride concentration is still obtained after deliberate addition of aluminium or iron in the form of their alums. Aluminium (III) and iron (III) form very strong fluoride complexes [70] and, provided that sufficient time is allowed for equilibration (as noted by Baumann [64] for very low fluoride concentrations), total flu-... 

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