Colorimetric Determination of Iron with 2,2'-Bipyridyl and with 2,2',2'-Terpyridyl

Molybdenum Blue Reaction: A Spectrophotometric Study

Publisher Summary This chapter discusses the various methods of analyzing the amount of boron present in plants and soil. The early methods of analysis for boron were designed chiefly to detect large amounts and involved separation and estimation by gravimetric or volumetric procedures. Typical of these procedures are those that involve the distillation of the methyl ester of boric acid followed by titration or weighing. Some of these procedures include titrimetric procedures, spectroscopic methods, colorimetric methods, and biological methods. The chapter also discusses various factors affecting the availability of boron in soil and the requirement of boron in plants. Although it has been found that boron availability is decreased in many cases by an excess of lime, the greatest areas of boron deficiency are found in the humid regions where the soil is generally acidic. Another factor that contributes to the loss of boron in soil is leaching. Boron plays a major role in the development of plants. It is essential to cell division in the meristematic tissues and in the cambium. Boron deficiency leads to the death of the terminal growing point of the stem, breakdown of the conducting tissues of the stem, brittleness of the stem and petiole, and an extremely poor growth of roots, which tend to develop an unhealthy brownish color.

Boron in Soils and Crops

The first fifty years of the chemistry of 2,2'-bipyridine are reviewed from its first discovery in 1888 to the outbreak of the second global conflict in 1939. The coordination chemistry and analytical applications are described and placed in the context of the increasingly sophisticated methods of characterization which became available to the chemist in this time period. Many of the "simple" complexes of 2,2'-bipyridine reported in the early literature have been subsequently shown to have more complex structures.

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The Early Years of 2,2'-Bipyridine-A Ligand in Its Own Lifetime

Some earlier research and the developments which led to the discovery of the essentiality of silicon for warm blooded animals are reviewed, and pitfalls in the methodology of silicon determination in biological material are described with special reference to germanium as an interfering factor in the ammonium molybdate reaction. Previous work from our laboratory on the occurrence of bound silicon in connective tissue components such as glycosaminoglycans is reviewed. It was based partially on results obtained with materials which were contaminated by silica or polysilicic acid. The total amount of silicon in ground matrix and connective tissue is smaller than assumed earlier. Thus, the hypothesis that silicon acts as a cross-linking agent in the ground matrix may have to be modified. Silicic acid derivatives may function in this fashion in special organelles such as base membranes, micro-tubules, etc. In the formation of organic silic acid derivatives, i.e., silanolates or silicic acid esters, not only the hydroxyl groups of carbohydrate derivatives, but also the hydroxyamino acids or other hydroxyl groups may serve as potential carriers of the silicic acid residue. In such structures, donation of electrons by amino N, leading to penta- or hexa-coordinated derivatives may have a stabilizing effect.

Significance and Functions of Silicon in Warm-Blooded Animals. Review and Outlook

Molybdat liefert mitαα′-Dipyridyl und dann mit Zinnchlorur versetzt, eine tief rotviolette Farbung, die zum Nachweis von Molybdan dienen kann. Diese Reaktion wird auf das Auftreten eines niedrigeren Molybdanoxyds im Verlaufe der Reduktion durch Zinnchlorur zuruckgefuhrt. Die Storung dieses Nachweises durch Wolframat kann durch Komplexbildung mit Weinsaure behoben werden.

Über eine Farbreaktion auf Molybdän mitα-α′-Dipyridyl

Über eine neue Tüpfelreaktion des Berylliums

Der Nachweis kleiner Germaniummengen mit Hilfe einer Tüpfelreaktion

Eine empfindliche Reaktion auf Borsäure

Die vonF. Feigl aufgefundene Fahigkeit von Persaurebildnern, die normalerweise zu Tetrathionat fuhrende Umsetzung zwischen Thiosulfat und Wasserstoffsuperoxyd unter Sulfatbildung abzulenken, last sich auch zum Nachweis von Niob und Tantal verwenden, da diese Erdsauren gleichfalls Persauren zu bilden vermogen. Durch diese Katalysenreaktion lassen sich bei Verwendung eines geeigneten Reaktionsgemisches an der Bildung von Bariumsulfat in 4 ccm Losung 0,2γ Nb und 0,4γ Ta erkennen. Komplexe Niob- und Tantalverbindungen reagieren in gleicher Weise.

A. S. Komarowsky

Papers

Über eine Farbreaktion auf Molybdän mitα-α′-Dipyridyl

Über eine neue Tüpfelreaktion des Berylliums

Der Nachweis kleiner Germaniummengen mit Hilfe einer Tüpfelreaktion

Eine empfindliche Reaktion auf Borsäure

Über einen empfindlichen katalytischen Nachweis von Niob und Tantal