The determination of fluorine by the lead chlorofluoride method in compounds containing halogens, sulphur, phosphorus and arsenic

Belcher, R.; Caldas, E. Fernández; Clark, Stanley J.

doi:10.1039/an9527700602

Cited by 10 publications

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“…330 The lead chlorofluoride method for the determination of flporine has been adapted to provide a Volhard titration finish. 331 Oxalic acid may be titrated with permanganate at room temperature in the presence of ferric a l ~m . ~3 ~ Tartaric acid has been determined by treatment with excess of standard sodium vanadate solution and back titration with standard iron(I1) solution.333 A method has been described which is suitable for the simultaneous determination of aldehydes, ketones, and compounds such as a ~e t a l s , ~~~ and methods for carbonyl compounds have been critically e~amined.33~ The necessity for close tolerances on the standard glass joints in methoxyl apparatus has been stressed.336 A modification has been proposed for the van Slyke apparatus for determining amino-groups in which carbon dioxide is used as a sweeping gas.…”

Section: Specifications Have Been Drawn Up For Apparatus For the Comb...mentioning

confidence: 99%

Analytical chemistry

Wilson¹

1952

Annu. Rep. Prog. Chem.

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Section: Specifications Have Been Drawn Up For Apparatus For the Comb...mentioning

confidence: 99%

Analytical chemistry

Wilson¹

1952

Annu. Rep. Prog. Chem.

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A new lead chlorofluoride method for the determination of fluorine in organic compounds

Belcher

Maedonald

1957

Mikrochim Acta

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Some years ago, a gravimetric method for the determination of fluorine in organic compounds was described1; this was based on decomposition of the compound by fusion with alkali metal in a nickel bomb followed by precipitation as lead chlorofluoride. The method has given very satisfactory results under routine conditions but, as was indicated previously, it suffers from the limitation that good results can only be obtained if more than 25 mg of fluoride are present. When only small samples are available, we use a thorium nitrate micro-titration ~, which gives results of similar accuracy but is less preferable than the lead chlorofluoride method for routine use because the end-points, as in all thorium nitrate titrations, give trouble to unpractised operators.The solubility losses which occur when less than 25 mg of fluoride are present in the previous lead chlorofluoride method 1 can be reduced by decreasing the volume of lead chloride precipitant added, but the method is not then applicable over a sufficiently wide range. Since the deficiency of the precipitant lies in its comparatively low lead content, it seemed possible that lower amounts of fluoride could be precipitated quantitatively if an equimolecular solution of lead and chloride were used. This would also be more likely to give a precipitate of the theoretical composition. Contrary to expectation, we found that lead chloride dissolves slightly more readily in lead nitrate solutions than in water; there is some evidence s, ~ that a salt, PbCINO~, is formed. Thus the lead concentration can be increased almost indefinitely without fear of precipitating lead chloride. * This paper is dedicated to Professor Dr. Hans Lieb, former ~eacher of R. B., on the occasion of his 70th birthday.

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The microanalysis of fluorine-containing organic compounds

Belcher

Macdonald

1956

Mikrochim Acta

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The procedure for the decomposition of organic compounds containing fluorine described in the previous papers of this series1, 2 has now been extended to the determination of sulphur. The compound is fused with sodium metal at 600~ in a nickel bomb and the sulphide formed is oxidised to sulphate. The latter is then precipitated as barium sulphate which is evaluated by a titrimetric method 3.We have again preferred titrimetric to gravimetric methods for the completion of the determination, for they are generally more suited to routine analysis. 4-Amino-4'-chlorodiphenyl, which has recently been proposed as a reagent for the determination of sulphur in organic compounds after conventional methods of decomposition 4, would not be applicable in the presence of the phosphate ions which would be produced when phosphorus-containing compound~ are decomposed. Because we intended to develo p a method which could be applied to the widest possible range of compounds, we precipitated the sulphate ion as barium sulphate; this is the only procedure available which can be applied to compounds containing phosphorus. We have shown that a recent titrimetric method for the evaluation of precipitates of'barium sulphate a is satisfactory on the microscale. After filtration on a paper pulp pad,

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The determination of fluorine by the lead chlorofluoride method in compounds containing halogens, sulphur, phosphorus and arsenic

Abstract: A piece of platinised platinum foil, 0.5 X 0.5 inch, fused near the end of a glass rod.

Cited by 10 publications

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Analytical chemistry

Analytical chemistry

A new lead chlorofluoride method for the determination of fluorine in organic compounds

The microanalysis of fluorine-containing organic compounds

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