Molecular emission cavity analysis (meca)—a new flame analytical technique: Part III. The determination of boron

Two highly selective methods are described for the determination of boron by molecular emission cavity analysis. In one, boron (>0.1 p.p.m.) is extracted as its 2-ethylhexane-1,3-diol chelate into methyl isobutylketone; 5-80 ng of boron in 5 μl of the extract is determined by injection into the MECA cavity. In the other, boron (2-30 μl) is converted into volatile methyl borate, and carried into the rear of the cavity by a stream of nitrogen. In both methods, the emission intensity at 518 nm, stimulated by a hydrogen-nitrogen-oxygen flame, is measured. Of the other ions tested, none interfered in the volatilization procedure, and only fluoride ( ? 100 mg) interfered in the extraction method. The precision is ±4%.     

Photometric titration of small quantities of metals with ethylenediaminetetra-acetic acid

A commercially available photometric titration apparatus has been used for the determination ofAl, Ba, Bi, Ca, Cd, Co, Mg, Mn, Ni and Zn in the 4-20 mug range and of Hg in the 16-32 mug range. Pooled standard deviations (32 determinations) of between 0.09 and 0.15 mug were found for all the metals except Ba (0.20 mug) and Hg (0.44 mug, 24 determinations).     

Titrimetric methods for the micro determination of sulphur and halogens in organic compounds by the rapid combustion procedure : The simultaneous determination of sulphur and the halogens

The quantitative absorption of the gaseous products arising from the oxidative degradation of organic materials containing sulphur, halogens, (chlorine, bromine and iodine) oxygen and nitrogen, by the rapid empty tube combustion has been studied further. Satisfactory titrimetric methods for the simultaneous determination of sulphur and any one or two of the halogens in the presence or absence of nitrogen have been developed.     

The titrimetric determination of carbon dioxide with special reference to the determination of carbon in organic compounds

The titrimetric barium carbonate method for the determination of. carbon in organic compounds has been examined and the various sources of error are discussed. The carbon dioxide from the combustion of the sample is absorbed in excess baryta containing 20% (w/v) barium chloride and the excess is back-titrated with hydrochloric acid in the presence of o-cresolphthalein indicator.The value of this method in conjunction with the previously described determination of water with succinyl chloride, for the simultaneous determination of carbon and hydrogen is assessed     

The micro-determination of chloride ion using an amplification procedure

Summary A comparative study has been made of the use of silver iodate, mercurous iodate and mercuric iodate for the determination of the chloride ion on the micro scale. The principle of the method is that the sparingly-soluble iodate reacts with the chloride ion to produce an equivalent amount of iodate ion. After filtration of the solution the iodate ion is titrated iodometrically, a six-fold amplification of titre being obtained.All three of the reagents give results of similar accuracy. Mercuric iodate is slightly superior in this respect to the other two reagents, but has the disadvantage that it cannot be used in acidic solutions. The results obtained are very reproducible, but deviate up to two per cent from the theoretical, depending upon the chloride ion concentration in the range 0.7–3.5 mg.

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Zusammenfassung Es wurden vergleichende Untersuchungen über die Verwendung von Silber-, Quecksilber(I)- und Quecksilber(II)-Jodat zur Mikrobestimmung von Chlorionen durchgeführt. Das Prinzip der Methode beruht auf der geringen Löslichkeit dieser Jodate, die mit Chloridionen unter Bildung äquivalenter Mengen freier Jodationen reagieren. Nach Filtration der Lösung werden diese jodometrisch titriert, wobei sich der sechsfache Titer ergibt.Alle drei Reagenzien geben Resultate ähnlicher Genauigkeit. Quecksilber(II)-Jodat ist den beiden anderen Salzen etwas überlegen, hat aber den Nachteil, daß es in saurer Lösung nicht verwendbar ist. Die Ergebnisse sind gut reproduzierbar, liegen aber bei Anwendung von 0,7 bis 3,5 mg Chloridionen bis zu 2% über der Theorie.

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Résumé On a fait une étude comparée pour l'emploi de l'iodate d'argent, de l'iodate mercureux et de l'iodate mercurique pour le dosage de l'ion chlorhydrique à l'échelle micro. Le principe de la méthode est que l'iodate peu soluble réagit sur celui-ci pour produire une quantité équivalente d'ion iodique. Après filtration de la solution, ce dernier est dosé iodométriquement, ce qui amplifie le titre de six fois. Ces trois réactifs donnent des précisions du même ordre. L'iodate mercurique est légèrement supérieur aux deux autres à cet égard mais il présente l'inconvénient de ne pouvoir servir en solution acide. Les résultats obtenus sont très reproductibles mais s'écartent de 2% au maximum de la théorie suivant que la concentration en ion chiorhydrique est comprise dans le domaine 0,7–3,5 mg.

     

Some factors influencing the solubilities of amine sulphates

The relationship between the molecular structures of amines and the solubilities of their sulphates has been examined with the object of finding a better reagent than benzidine for the determination of sulphate. It has been established that the two aromatic rings must have a tendency to be coplanar and collinear, if the sulphate solubility is to be low. With the help of this theory, 4 : 4'-diaminotolane sulphate has been found to be less soluble than bcnzidine sulphate.     

Application of the integrated ion-current technique to the study of rare-earth chelates

Several substituted acetylacetones have been prepared and reacted with holmium to give tris chelates of the form HoL₃. One of these chelates has been converted to a tetrakis chelate of the form NaHoL₄. The mass spectra of these compounds have been studied and the integrated ion currents at significant m/e values have been related to the amounts of metal chelates evaporated into the ion source of the mass spectrometer. The shape of the integrated ion-current curve is shown to give information about the nature of the evaporation process. When the β-diketone (L) is asymmetrical as in the case of 1,1,1-trifluoro-5,5-dimethylhexan-2,4-dione, the existence of geometrical isomers of the chelate, HoL₃, is reflected in the shape of the integrated ion-current curve, which shows fine structure. The results of mass spectrometric studies are compared with those of the sublimation and gas chromatographic behaviour of the metal chelates.     

Some observations on the precipitation of group II metals in qualitative analysis

Difficulties in the precipitation of Group II of the classical scheme of qualitative inorganic analysis are discussed. Three reagents for the destruction of permanganate and dichromate have been examined; hydrogen peroxide was found to be most suitable. Conditions have been established whereby As₂S₅ can be precipitated, thus avoiding the necessity for reducing As^V before passing hydrogen sulphide. A simple separation of the Group IIB elements, based on the stepwise precipitation of their sulphides from solutions of controlled acidity, is proposed.These modifications have been adapted to the procedures of Holness² and Holness and Trewick¹, for adjusting the acidity and for dividing the sulphide precipitates into the two sub-groups.     

The effect of ethylenediaminetetraacetic acid on the ferrous/ferric and cuprous/cupric redox systems

The effect of ethylenediaminetetraacetic acid on the redox systems Fe⁺²/Fe⁺³ and Cu⁺/Cu⁺² has been examined. In each case the oxidation potential of the system was markedly reduced, thus making the lower valency state a more powerful reductant. It has been established that the oxidation potentials of the two systems, in the presence of EDTA, at PH 4–5, are 0.12 and 0.13 v respectively.Because of these enhanced reducing powers, attempts were made to use ferrous-EDTA and cuprous-EDTA as reductimetric reagents. A variety of oxidants was in fact successfully titrated, but neither titrant possessed any advantage over existing reagents.The reducing properties of both systems lie intermediate between those of stannous and titanous chlorides.Theoretical considerations suggest the existence of a cuprous-EDTA complex with a formation constant of ca. 10¹⁸.