Higher iron fluorides

The values of AH for the thallium (III) halide systems becomes less exothermic as complex formation proceeds. There are no steps with about the same value of AH , in marked contrast to e.g. Hg2+ and Pd2+. The trend of AH is in fact opposite to that found for several t)q)ical hard-hard interactions, e.g. iron (III) fluoride, lanthanum sulphate and yttrium acetate (Table 1). An even more striking feature of the thallium (III) halides is that AS°n is approximately constant for all steps. This is indeed different not only from ions such as In +, Cd2+ and Zn +, where reversals of the decreasing trend of AS°n occur for certain steps, but also from Hg2+ and Pd + where the higher steps have a much lower value of ASn than the earlier ones. 

Oxidation states IV to VIII inclusive are represented in the fluorine chemistry of osmium, as compared with III to VI for ruthenium and II and III for iron. Thus the fluorides of the iron-ruthenium-osmium triad well exemplify the greater tendency of second and third row elements to higher oxidation states with rc-donor ligands. 

Higher temperatures (100-125°) are employed when carboxyl or nitro groups.are on the nucleus. Benzenesulfonyl fluoride is obtained in 62% yield by the action of excess fluorosulfonic acid at 20° on benzene in an iron vessel. ... 

The absorbance of the Co(III) complex solution may be measured with higher sensitivity at 415-425 nm, or with lower sensitivity at 500-520 nm (a reagent blank, or water as reference). The reaction of cobalt with nitroso-R salt is usually done in a hot weakly acidic medium buffered with sodium acetate. The solution is then made sufficiently acidic with hydrochloric or nitric acid to decompose the nitroso-R salt complexes of other metals (e.g., Cu, Ni, Fe, and Mn), which are less stable than the cobalt(III) complex. Phosphate or fluoride masks iron (III), which has a yellow colour in hydrochloric acid medium. 

One participant repeated its analysis with a higher combustion time and additional water steam and iron phosphate and found higher results than those previously submitted. Fluoride could not be found in the residue (verified by fusion) and was assumed to be lower than the detection limit, i.e. 20 mg kg. The three methods used were in good agreement (ISE after combustion, fusion/steam distillation, steam distillation). 

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