Color reaction analytical

Both arsonic and arsinic acids give precipitates with many metal ions, a property which has found considerable use in analytical chemistry. Of particular importance are certain a2o dyes (qv) containing both arsonic and sulfonic acid groups which give specific color reactions with a wide variety of transition, lanthanide, and actinide metal ions. One of the best known of these dyes is... 

The efficiency of the machinery employed is discussed, pertinent supporting analytical data are presented, and the sensitivity of the color reaction, leading to unbelievably easy contamination, is stressed. Over processing in all steps is recommended as a means of nullifying inherent variations in the efficiencies of different types of processing apparatus used by other workers. 

Ninhydrin, 22 101 Ninhydrin-color reaction amino acids, 2 570 Niobates, 27 152-153 24 315 Niobia-phosphate catalytic aerogels, 2 763t Niobic acid, 27 152 Niobic salts, 27 152-153 Niobium (Nb), 27.132-157 24 313, 315. See also Nb-Ti entries Niobium compounds Niobium metal analytical methods for, 27 142-144 dissolution methods for, 27 142 economic aspects of, 27 140-142 effect on stainless steel corrosion resistance, 7 809... 

Various international pharmacopoeias help assure the quality of drugs worldwide. These pharmacopoeias constantly review and revise their monographs. A different impurity profile can be anticipated if a drug s production process is changed this results in the development of new analytical methods that need to be incorporated in the pharmacopoeias. In earlier editions, color reactions were performed for identification and purity evaluation purposes. 

Color reactions are chemical reactions that produce colored products. Identification of a compound, or more commonly a group of compounds, by color reactions is one of the oldest and simplest methods in analytical chemistry. It is based on the fact that a specific compound or a group of compounds, when treated by an appropriate reagent (often called color reagent ), produce a color that is characteristic of this compound or group of compounds. 

Recalling the above-mentioned classification of color reactions, it is clear that in the Griess reaction atoms from the analyte are incorporated into the colored product. This leads to a higher degree of specificity compared with oxidation/ reduction reactions where only electrons (and no atoms) are transferred. 

In forensic laboratories, chemical spot tests based on color reactions, have been replaced over the years by modem, more accurate instrumental methods. However, analytical techniques based on color formation are stiU commonly employed in field tests for explosives. Being inexpensive, simple, easy-to-operate and often quite sensitive (see above), they are most suitable for use outside the laboratory as presumptive field tests for the presence of explosives. 

Encyclopedia 3(PATR 2700) (1966), pp C275 to C288 (Chromates and Dichromates, Including Their Analytical Procedures) C411 to C417 (Analytical Procedures Based on Color Reactions. Rapid Method... 

Color reactions and color reagents 3 C405-C420 analytical procedures based on color reactions, a rapid method of identification of common expl compds and of expl mixtures 3C411-C417... 

Centralite 3, Analytical Procedures. Accdg to Kast-Metz(1944), 167, color reactions of Centr 3 are identical with those described under Centr 1. Some gravimetric and volumetric procedures described in Kast-Metz(l944), 292-3 are applicable to detn of Centr 3 in smokeless proplnts. No other info is at out disposal Centralite 3, Nitro Derivatives. No info at our disposal... 

Analytical Procedures Based on Color Reactions Rapid Method of Identification af Common Explosive Compounds and of Explosive Mixtures... 

Composition A Type Explosives, Analytical Procedures. Composition A-3.Colorimetric method of identification is described in this volume of Encyclopedia under Color Reactions and Color Reagents and also in Refs 2 7... 

TNT forms charge-transfer, or 7r, complexes with polycyclic aromatic hydrocarbons, aromatic amines, and aromatic nitro compds a number of these are listed below in Table 2. The complexes with three amines (diphenylamine, diethyl-aniline, p-anisidine) have characteristic colors this forms the basis for a rapid and convenient thin-layer chromatographic analytical procedure (Ref 34) for the identification of very small amounts of TNT. (For a discussion of the many color reactions of TNT, and of composite expls containing it, see Vol 3, C405-L ff)... 

In chemically based selectivity, the sensing information is usually obtained from the color reaction between the analyte X and the indicator molecule I forming a colored complex X I, in which either the indicator and/or the conjugate have characteristic absorption... 

Analytical Reagents. As a result of their fast and intense color reaction, formazans can be used for the spectroscopic determination of a variety of metal ions. In a sensitive blue color reaction, Zn and Cu can be determined with the commercial reagent Zinkon (46 [135-52-4]). The detection limit for Zn (Xmax = 625 nm) is 0.02 ppm. 

The nineteenth century also produced reagents for the one-electron oxidation of suitable substrates. For example, sulfuric acid was employed for many years as an analytical reagent because of some color reactions. Thus, Laurent treated benzimid , C28H10O2+HAz, a residue from the oil of bitter almonds (ben-zaldehyde) and observed an indigo blue solution [34]. On the other hand, the blue solution observed by Liebermann upon treatment of chrysene with sulfuric acid can be attributed to the chrysene radical cation [43]. 

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