A.G. Fogg

Use of basic dyes in the determination of anions, particularly as a means of determining antimony, thallium, and gallium.

The use of xanthene, triphenylmethane and other basic dye cations as reagents for the determination of anions is reviewed. Elements and anions determined include Sb, Tl, Ga, Au, Te, In, Zn, Ta, Hg, Re, Sn, U, Os, B, Cr, Ag, ClO(4)(-), PO(4)(-), SO(4)(2-) and NO(3)(-). Difficulties encountered in developing satisfactory procedures involving basic dyes are discussed. Procedures for the purification and analysis of basic dye samples are outlined.

Analytical aspects of organo-P, As, Sb, S, Se, Te and Sn(IV) (onium) cations

Reactions and the analytical applications of tetraphenyl-phosphonium, -arsonium and -stibonium, triphenylmethylarsonium, triphenyl-sulphonium, -selenonium and -telluronium and triphenyltin cations with oxy-anions, and halo- and thiocyanato-anionic complexes are surveyed.

A critical study of Brilliant green as a spectrophotometric reagent: the determination of perrhenate and gold

The spectrophotometric methods for determining rhenium and gold with Brilliant green have been re-examined in an investigation of the effects of purity of reagent and acidity on the precision and accuracy of results. The perrhenate-Brilliant green ion-association complex is extracted from a solution at pH 6, and is unaffected by reagent purity. The extraction of the tetrachloroaurate(III)-Brilliant green ion-association complex is carried out from 0·5 M hydrochloric acid solution, however, and an impure reagent gives low recoveries. Procedures are recommended for the determination of rhenium and gold, and the purification of the reagent is discussed.

The boedeker reaction—I: The interaction of alkali metal sulphites and nitroprussides in aqueous solution☆

Abstract The association of nitroprusside and sulphite ions in aqueous solution has been shown colorimetrically to be greatly affected by alkali metal ions. An increase in alkali metal ion concentration intensifies the red colour characteristic of the sulphitonitroprusside ion, Fe(CN)5NOSO34−. Further, for equivalent concentrations of alkali metal ion, the extent of intensification increases with the size of the alkali metal ion. It is suggested that the sulphitonitroprusside ion exists in solution mainly as the ion pair, Fe(CN)5NOSO3M3−, where M is an alkali metal. The stability constants for this system are considered. The values obtained indicate that the degree of association is much lower than has previously been reported.

A critical study of Brilliant green as a spectrophotometric reagent: the determination of perchlorate particularly in potassium chlorate

A modified procedure for the extraction of perchlorate with Brilliant green into benzene is described, which gives a reproducible and nearly quantitative recovery of perchlorate (apparent Iµ640nm= 94 000) and low blanks (A= 0·02 to 0·04). Studies on the use of untreated glassware, silanised glassware and polypropylene-ware have indicated that adsorption effects are not very important. Nevertheless, the standard and sample solutions should be treated in the same vessels and the absorbance measurements made in quartz cells.Brilliant green perchlorate can be extracted from aqueous solutions in the pH range 3 to 6·5, but the solutions should be buffered at a constant pH value.The procedure has been applied successfully to the determination of perchlorate in samples of potassium chlorate.

The spectrophotometric determination of tungsten with thiocyanate. Part I. A review of procedures

Existing procedures for the determination of tungsten with thiocyanate are reviewed and compared.

A critical study of Brilliant green as a spectrophotometric reagent: the determination of antimony

The spectrophotometric method of determining antimony with Brilliant green has been re-examined in an investigation of a suspected variability of samples of Brilliant green. The reaction conditions and times have been shown to be critical and a modified procedure, which gives a higher sensitivity and precision compared with previous procedures, has been developed. It is considered doubtful whether an entirely satisfactory method of determining antimony with Brilliant green can be developed.

Applications of sensitised reactions. Spectrophotometric determination of tin in steel with catechol violet and cetyltrimethylammonium bromide

Modification of the visible spectrum of the catechol violet-tin(IV) complex by the addition of surfactants and basic dyes has been studied in an attempt to improve the catechol violet procedure for determining tin. On adding cetyltrimethylammonium bromide, the cetyltrimethylammonium salt of the catechol violet-tin(IV) complex anion is probably formed in colloidal solution and dispersed by the excess of the surfactant. The Brilliant green cation reacts with the complex anion in a similar manner and the salt formed can be dispersed with poly(vinyl alcohol). In the latter instance, however, the bathochromic shift in the main absorption band of the complex is not associated with increased sensitivity.The spectrophotometric method of determining tin with catechol violet and cetyltrimethylammonium bromide has been modified and applied to the determination of tin in steel. Preliminary separation of tin is achieved by extracting tin(IV) iodide into toluene. Results obtained with a wide range of British Chemical Standard steels indicate a high precision for the recommended procedure. Lactic acid is used to mask molybdenum, chromium, vanadium, nickel and cobalt, which interfere at the levels that are commonly found in steels. The recommended procedure is not applicable to steels with copper to tin ratios greater than 20 : 1 owing to precipitation of copper(I) iodide at the extraction stage.

The spectrophotometric determination of tungsten with thiocyanate. Part II. An experimental assessment of procedures: a recommended procedure for the determination of tungsten in steel

The precision, sensitivity, colour stability and selectivity of several procedures for the spectrophotometric determination of tungsten with thiocyanate have been compared.An extraction procedure in which tetraphenylarsonium or similar ions are used for the determination of tungsten in steel has been developed, which has shown consistent reliability when applied to a wide range of tungsten steels, and which is completely free from interference by vanadium. The concentration of iron in the aqueous solution from which the tungsten is extracted determines the extent of interference by molybdenum. When the recommended sample size and dilution factors are used, 0·3, 3·0, 12, 60 and 97·5 per cent. w/w of molybdenum can be tolerated for tungsten in the ranges up to 0·25, 0·25 to 0·5, 0·5 to 1·25, 1·25 to 2·5 and 2·5 to 25 per cent. w/w, respectively. The tolerances in the lower tungsten ranges can be increased if necessary by using a higher dilution factor and accepting a lower absorbance reading.

Some studies of the colorimetric determination of tin in steel: The effect of dispersing agents

ZusammenfassungEin Überblick über colorimetrische Zinnbestimmungsmethoden in Stahl wird gegeben und Vorschläge zur Abtrennung des Zinns, der Maskierung störender Metalle sowie der Auswahl des colorimetrischen Meßverfahrens gemacht. Der Einfluß von Dispergierungsmitteln auf die Eeagentien und gebildeten Komplexe wird diskutiert, wobei über neue Untersuchungen zum Einfluß von Cetyltrimethylammoniumbromid auf das System Phenylfluoron/Zinn(IV) berichtet wird.SummaryA survey of existing procedures for the colorimetric determination of tin in steel is given. Recommendations are made with regard to separating tin, masking interfering metals and selecting a colorimetric finish.The effect of dispersing agents on reagents of the type used for determining tin, and on the complexes formed in these determinations, is discussed, including new work on the effect of cetyltrimethylammonium bromide on the phenylfluorone-tin(IV) system.