Colorimetric reagents

Sulfosahcyhc acid is prepared by heating 10 parts of sahcyhc acid with 50 parts of concentrated sulfuric acid, by chlorosulfonation of sahcyhc acid and subsequent hydrolysis of the acid chloride, or by sulfonation with hquid sulfur trioxide in tetrachloroethylene. It is used as an intermediate in the production of dyestuffs, grease additives, catalysts, and surfactants. It is also useful as a colorimetric reagent for ferric iron and as a reagent for albumin. Table 9 shows the physical properties of sahcyhc acid derivatives. 

Diphenylcarbazide as adsorption indicator, 358 as colorimetric reagent, 687 Diphenylthiocarbazone see Dithizone Direct reading emission spectrometer 775 Dispensers (liquid) 84 Displacement titrations 278 borate ion with a strong acid, 278 carbonate ion with a strong acid, 278 choice of indicators for, 279, 280 Dissociation (ionisation) constant 23, 31 calculations involving, 34 D. of for a complex ion, (v) 602 for an indicator, (s) 718 of polyprotic acids, 33 values for acids and bases in water, (T) 832 true or thermodynamic, 23 Distribution coefficient 162, 195 and per cent extraction, 165 Distribution ratio 162 Dithiol 693, 695, 697 Dithizone 171, 178... 

Figure 17-1. Colorimetric reagent to measure zirconium in geis.

The concentration of an oxidative gel breaker can be measured by colorimetric methods, by periodically or continuously sampling the gel [341]. The colorimetric reagent is sensitive to oxidizing agents. It contains iron ions and thiocyanate. Thus the quantity of breaker added to the fracturing fluid can be controlled. 

In addition to the chemical effects of varying salinity, there are optical interferences in colorimetric analysis which are peculiar to estuarine samples. Saline waters and river waters have, in the absence of colorimetric reagents, an apparent absorbance arising from ... 

The addition of halcinonide to various colorimetric reagents gives results typical of steroids with its... 

We have shown a new concept for selective chemical sensing based on composite core/shell polymer/silica colloidal crystal films. The vapor response selectivity is provided via the multivariate spectral analysis of the fundamental diffraction peak from the colloidal crystal film. Of course, as with any other analytical device, care should be taken not to irreversibly poison this sensor. For example, a prolonged exposure to high concentrations of nonpolar vapors will likely to irreversibly destroy the composite colloidal crystal film. Nevertheless, sensor materials based on the colloidal crystal films promise to have an improved long-term stability over the sensor materials based on organic colorimetric reagents incorporated into polymer films due to the elimination of photobleaching effects. In the experiments... 

The colorimetric methods depend on a chemical reaction or interaction between the protein and the colorimetric reagent. The resulting generation of a chro-mophore, whose intensity is protein-concentration dependent, can be quantified using a spectrophotometer. Beer s Law is employed to derive the protein concentration from a standard curve of absorbances. Direct interaction of the protein with a chromogenic molecule (dye) or protein-mediated oxidation of the reporter molecule generates a new chromophore that can be readily measured in the presence of excess reagent dye. 

In an automatic instrument developed by Lidzey and Stockwell [19] for the analysis of ftirftiraldehyde in gas oil, a preliminary separation is performed on a GC column coupled to a specific colorimetric reagent in a continuously flowing hquid stream. A back-flushing... 

Measurement of trace metals, including nickel in seawater can be completed using an in-line system with stripping voltammetry or chronopotentiometry (van den Berg and Achterberg 1994). These methods provide rapid analysis (1-15 minutes) with little sample preparation. The detection limit of these methods for nickel was not stated. Recommended EPA methods for soil sediment, sludge, and solid waste are Methods 7520 (AAS) and 6010 (ICP-AES). Before the widespread use of AAS, colorimetric methods were employed, and a mrmber of colorimetric reagents have been used (Stoeppler 1980). 

Ethylenediamine, as such, is used as a solvent for various compds, as a corrosion inhibitor in antifreeze soln, stabilizer in rubber latex, etc. Its use as a colorimetric reagent for expls, such as TNT, etc, is discussed in Vol 3 of Encycl, p C406 L Refs 1) Beil 4, 230, (398), [676] 1478 ... 

The reactions of alcohols related to phenolphthalein and fluorescein with Ag1 ions have been investigated for their application as colorimetric reagents in determining trace amounts of silver. A simple, rapid and sensitive method was found which used 2,4,5,7-tetra-bromofluorescein and 1,10-phenanthroline. A ternary complex was formed with a deep pink colour (Ama 550 nm) in the presence of silver(I) ions and the two reagents. No significant colour change was observed in the absence of the diimine.227... 

The reactions of silver(I) with 1,5-diphenyl thiocarbazone (56 dithizone = HaDz) by comparison to thiosemicarbazones have been thoroughly investigated.442,444 Dithizone has for many years been used as a colorimetric reagent for trace metal ions. Its metal complexes are of two types, the so-called primary and secondary dithizonates. Primary dithizonates are generally formed at low pHs where the ligand becomes mono depronated (pA = 4.5) but retains the NH proton. Secondary dithizonates are formed in the presence of an excess of metal and/or at higher pH values where the ligand becomes fully deprotonated. Since it has been estimated that for free dithizone pK2 > 15, the second proton obviously becomes labilized in the presence of metal ions. 

The following colorimetric reagents are commonly used in explosives laboratories ... 

III. Treatment with Thymol Reagent. See item Q under colorimetric reagents and Charts A B given in this section... 

V. Treatment with Diphenylamine Reagent. See item E under colorimetric reagents and Charts A Si B. A yel color indicates the presence of one of the expls TNT, TNAns, HNDPhA, PA, AmmPic or DNPh viol, blue or black color indicates DNT, DNB, DINA, Tetryl, PETN, RDX, EDNA, EDD or AN red color indicates o-MNN... 

XII. Treatment with Nessler s Reagent. Prepn of reagent is described as item M under colorimetric reagents. For test, prep a satd soln of sample by shaking ca O.lg with ca 3ml of w. 

TNT with ca 1% of wax(See this vol under Composition B Type Explosives and Cyclotols) gives positive reactions with colorimetric reagents used for inentification of RDX or TNT by warming... 

When a determination is critical, it is often necessary to do two or more different colorimetric tests in parallel. A substance present in the sample could interfere with one test while not affecting others. In most cases, interference can be controlled. Interference can be detected by adding a known amount of sugar to a sample solution to be measured. The amount of sugar will differ from what is expected if there is interference. In addition, a very colored sample can interfere with the results obtained. In the case of colored samples, subtract the absorbance of the samples dissolved in water or buffer alone from the value obtained after addition of the colorimetric reagents. 

Bartroli, M Escalada, CJ Jorquera, J Alonso. Determination of total and free sulfur dioxide in wine by flow injectionp-aminoazobenzene as the colorimetric reagent. Anal Chem 63 2532-2535, 1991. 

A further interesting case is provided by the synthesis of ninhydrin (Expt 5.99, cognate preparation) from indane-l,3-dione (Expt 7.9) in which the methylene group is activated by two adjacent carbonyl groups. Ninhydrin is the stable monohydrate of the triketone, indane-l,2,3-trione, and is a well-known colorimetric reagent for amino acids (Section 2.31). 

To prepare the colorimetric reagent, sulfuric acid (250 ml 2.5 M) is added to ammonium molybdate (75 ml) and mixed. Then, ascorbic acid (50 ml) is added and mixed, followed by antimony potassium tartrate (25 ml) and further thorough mixing. The volume is finally adjusted to 500 ml. 

These tests were considered to be inconclusive, and the sensitivities of the colorimetric reagents used were not adequate to reliably detect the low concentrations found in actual firings.125-129... 

Reddy et al. described two spectrophotometric methods for nimodipine in its dosage forms [2]. The first method involves the use of para dimethylaminocinnamaldehyde as a colorimetric reagent, and the measurement of the generated color at 510 nm. The second method is... 

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