Testing Spectroscope

Aldridge et al. have demonstrated that a similar boryl-ferrocene 81 can be used as a selective colorimetric sensor for F . When F was added to a GH2CI2 solution of 81, under aerobic conditions, a color change from orange to pale green was observed. This did not occur with any other anion tested. Spectroscopic and electrochemical measurements suggest that complexation of F causes the spontaneous formation of a ferrocenium species, that is, the 150 mV anodic shift in the Fc/Fc redox potential caused by F complexation lowers the redox potential enough for the 81 2F complex to be aerobically oxidized. 

The pure white residue consists of RbCl, KCl, CsCl and SiOg. It is repeatedly extracted with hot water, and the silicic acid is filtered off. The filtrate is evaporated to dryness. To separate KCl and RbCl from CsCl, 16 g. of dry residue is dissolved in 40 ml. of warm 2.5N HCl and treated with 50 ml. of warm 96% alcohol. After cooling, the first KCl-RbCl precipitate is filtered off and the filtrate is heated and again treated with 300 ml. of warm 96% alcohol. Upon cooling, the second RbCl-KCl precipitate is filtered off and the filtrate once more treated with 50 ml. of alcohol and filtered as above. The filtrate is evaporated the residue contains all the CsCl. It is dissolved In 20 ml. of 2.5N HCl and treated with 5 ml. of 20% SbCla solution in 7.5N HCl. After a while, the Cs precipitates out as the chloroantimonate. The concentration of RbCl in the entire resulting solution must not exceed 1 M following the addition of the SbCla, since otherwise rubidium chloroantimonate is coprecipitated. The cesium chloroantimonate is then placed in a boat and heated in a stream of HCl gas at 250°C. The SbCla distills off and the CsCl remains as a residue. It can be tested spectroscopically for K and Rb. 

The dry residue so obtained consists of RbCl-KCl and is combined with the second and third RbCl-KCl fractions previously obtained in the separation of CsCl by alcohol treatment. The combined residue is redissolved in 180 ml. of 2.5N HCl and once more treated with the silicomolybdate reagent. The latter is added in portions with vigorous stirring until complete precipitation results. The precipitate is washed twice (vigorous stirring) with 60-ml. portions of 2.5N HCl, filtered as above and dried. Finally, it is converted to the chloride and freed of SiOg. The purify of the resulting RbCl can be tested spectroscopically. 

The first tenet of our working hypothesis, that different reagents induced different reaction pathways for acetals, could be tested spectroscopically if the putative reactive intermediates could be detected. Toward that end a simple substrate, heptanal dimethyl acetal, was combined with various... 

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

Analytical and Test Methods. In addition to the modem spectroscopic methods of detection and identification of pyrroles, there are several chemical tests. The classical Runge test with HCl yields pyrrole red, an amorphous polymer mixture. In addition, all pyrroles with a free a- or P-position or with groups, eg, ester, that can be converted to such pyrroles under acid conditions undergo the Ehrlich reaction with p-(dimethylamino)henzaldehyde to give purple products. 

Sodium is identified by the intense yellow color that sodium compounds impart to a flame or spectroscopically by the characteristic sodium lines. The latter test is extremely sensitive, yet because many materials contain traces of sodium salts as impurities, it is not conclusive evidence of the presence of sodium in any considerable quantity. 

Biological, spectroscopic, and chromatographic methods have been used to assay vitamin A and the carotenoids. Biological methods have traditionally been based on the growth response of vitamin A—deficient rats. The utiUty and shortcomings of this test have been reviewed (52,53). This test has found apphcabiUty for analogues of retinol (54,55). Carotenoids that function as provitamin A precursors can also be assayed by this test (56). 

Spectroscopic methods such as uv and fluorescence have rehed on the polyene chromophore of vitamin A as a basis for analysis. Indirectly, the classical Carr-Price colorimetric test also exploits this feature and measures the amount of a transient blue complex at 620 nm which is formed when vitamin A is dehydrated in the presence of Lewis acids. For uv measurements of retinol, retinyl acetate, and retinyl palmitate, analysis is done at 325 nm. More sensitive measurements can be obtained by fluorescence. Excitation is done at 325 nm and emission at 470 nm. Although useful, all of these methods suffer from the fact that the method is not specific and any compound which has spectral characteristics similar to vitamin A will assay like the vitamin... 

Thermal Properties. The thermal stabiUty of cellulose esters is deterrnined by heating a known amount of ester in a test tube at a specific temperature a specified length of time, after which the sample is dissolved in a given amount of solvent and its intrinsic viscosity and solution color are deterrnined. Solution color is deterrnined spectroscopically and is compared to platinum—cobalt standards. Differential thermal analysis (dta) has also been reported as a method for determining the relative heat stabiUty of cellulose esters (127). 

Much of the experimental work in chemistry deals with predicting or inferring properties of objects from measurements that are only indirectly related to the properties. For example, spectroscopic methods do not provide a measure of molecular stmcture directly, but, rather, indirecdy as a result of the effect of the relative location of atoms on the electronic environment in the molecule. That is, stmctural information is inferred from frequency shifts, band intensities, and fine stmcture. Many other types of properties are also studied by this indirect observation, eg, reactivity, elasticity, and permeabiHty, for which a priori theoretical models are unknown, imperfect, or too compHcated for practical use. Also, it is often desirable to predict a property even though that property is actually measurable. Examples are predicting the performance of a mechanical part by means of nondestmctive testing (qv) methods and predicting the biological activity of a pharmaceutical before it is synthesized. 

ETAAS, SPECTROSCOPIC AND TEST DETERMINATION OF HEAVY METALS IN NATURAL OBJECTS AFTER THEIR PRECONCENTRATION BY ADSORPTION... 

Brombenztiazo (BBT) is known to be one of the best reagents for extraction-photometric determination of cadmium(II). The reagent also fonus complexes with Co(II), Cu(II), Fe(II), Ni(II), Zn(II). The aim of this work was to develop a solid-phase reagent on the base of BBT immobilized on silica gel for sorption-spectroscopic and visual test determination of Cadmium, and also for soi ption-atomic-adsoi ption determination of total heavy metals contents in natural waters. 

BBT solution on unmodified sorbents of different nature was studied. Silica gel Merck 60 (SG) was chosen for further investigations. BBT immobilization on SG was realized by adsoi ption from chloroform-hexane solution (1 10) in batch mode. The isotherm of BBT adsoi ption can be referred to H3-type. Interaction of Co(II), Cu(II), Cd(II), Ni(II), Zn(II) ions with immobilized BBT has been studied in batch mode as a function of pH of solution, time of phase contact and concentration of metals in solution. In the presence of sodium citrate absorbance (at X = 620 nm) of immobilized BBT grows with the increase of Cd(II) concentration in solution. No interference was observed from Zn(II), Pb(II), Cu(II), Ni(II), Co(II) and macrocomponents of natural waters. This was assumed as a basis of soi ption-spectroscopic and visual test determination of Cd(II). Heavy metals eluted from BBT-SG easily and quantitatively with a small volume of HNO -ethanol mixture. This became a basis of soi ption-atomic-absoi ption determination of the total concentration of heavy metals in natural objects. 

The sensitive and selective soi ption-spectroscopic and visual test-methods for detenuination of Pb(II), Zn(II), 0,0 and F" in water and food-stuffs were proposed in comparative with known DRS and VT methods. 

Spektralanalyse, /. spectrum analysis, spektralanalytisch, a. spectroscopic, spectro-metric. — adv. by spectrum analysis. Spektral-apparat, to. spectroscopic apparatus, -beobachtung, /. spectroscopic observation, -bereich, -bezirk, to. spectral region, -farbe, /. spectral color, spectrum color, -gegend, /. spectral region, -lampe, /. spectrum lamp, -hnie, /. spectrum line, spectral line, -probe, /. spectrum test, -rohr, n.. -rohre, /. spectrum tube, spectral tube, -tafel, /. spectrum chart, spectral chart. 

This test indicates the amount of metallic constituents in a crude oil. The ash left after completely burning an oil sample usually consists of stable metallic salts, metal oxides, and silicon oxide. The ash could be further analyzed for individual elements using spectroscopic techniques. 

Maher draws attention to the 1874 paper of Lecoq de Boisbaudran in which he announced the discovery of gallium, the first of Mendeleev s predictions to be confirmed. And this is, indeed, an important paper. One possible misconception should, however, be quashed immediately. De Boisbaudran did not discover gallium as a result of testing Mendeleev s prediction. Instead he operated quite independently by empirical means in ignorance of Mendeleev s prediction and he proceeded to characterise the new element spectroscopically. De Boisbaudran s findings were published in the Comptes Rendus. 

Alloy samples weighing either 100 or 25 g. were prepared by melting weighed amounts of lead and thallium together. The c. p. granular test lead, free from silver, gold and bismuth (Fisher Scientific Company), was indicated by spectroscopic examination to contain approximately 0-005 % iron, 0-001 % thallium and 0-001 % copper. The thallium used was supplied by the Varlacoid Company. Spectroscopic examination showed the presence of approximately 0-01 % lead, 0-005 % iron, and 0-001 % copper. 

Extensive quantum chemical calculations have been reported for sulfur-rich compounds in the past two decades. These calculations were used to investigate molecular structures and spectroscopic properties, as well as to understand the nature chemical bonding and reaction mechanism. Many high-level ab initio calculations were used for interpretation of experimental data and for providing accurate predictions of molecular structures and thermochemical data where no reliable experimental values are available. In recent years, density functional calculations have been extensively tested and used on many first- and second-row compounds. These proven DFT methods look promising for larger systems because for their computational efficiency. 

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