Copper reduction test

A positive result in the black copper reduction test, suggesting alcaptonuria, can follow the use of diatrizoate, iotalamate or iodipamide (320). 

Special Tests for Saccharides. The Copper-reduction Tests... 

The reaction is important in providing a useful internal indicator for copper reduction tests, such as that of Fehling, and simplifies the determination of an end-point in an estimation. 

Qualitative Analysis. Nitric acid may be detected by the classical brown-ring test, the copper-turnings test, the reduction of nitrate to ammonia by active metal or alloy, or the nitrogen precipitation test. Nitrous acid or nitrites interfere with most of these tests, but such interference may be eliminated by acidifying with sulfuric acid, adding ammonium sulfate crystals, and evaporating to alow volume. 

Knight and Allen. This is a copper reduction method for reducing sugars in white sugar up to 0.02%. It utilizes EDTA to determine excess unreacted copper. Tests undertaken in 1994 to extend the range of this method were unsuccesshil. In spite of poor performance in ring tests, it remains an official ICUMSA method. 

Another procedure which has adequate sensitivity for determining the glucose in 1 microliter of serum of filtrate, is the method which uses copper reduction, and subsequently determination of the cuprous ion with a suitable reagent (15) However, one must be careful that one has obtained complete precipitation, for, if uric acid or any other impurities remain, false high values will be obtained. This would result in disaster for the hypoglycemic infant. To uncover this condition is often one of the major reasons for doing this test. 

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

Urine samples containing beta-lactams shonld be tested for glucose by the glncose oxidase method, since falsely high values are observed with the copper reduction method (366,367). 

When comparing the TPR profiles with the light-off curves from the ethanol oxidation experiments, we have foimd an indication of a correlation between activity and reducibility of the catalyst. Copper oxide supported on titania is the most active towards ethanol oxidation among the copper oxides tested. It is also the catalyst in which the reduction starts at the lowest temperature. The results obtained in the TPR experiments strengthen the hypothesis that there is a considerable interaction between the support and the active material. 

If the conversion products are tested polariscopically, it will be found that there will be a progressive fall in specific rotation values from that of starch paste (202°) to that of dextrose (52.70). The Fehling test shows no copper reduction with starch paste, at the beginning of the hydrolysis, but progressively increases till the maximum reducing power is reached when all of the converted products are finally transformed into dextrose. 

The British Pharmacopoeia, 1948 revision, includes standards for total ash, acid-insoluble ash, and starch and foreign organic matter. It requires certain identification tests— for instance, that no pink color is produced when tragacanth is treated with ruthenium red and that the characteristic copper reduction of alkaline copper tartrate solutions is produced to indicate the sugar character of the gum. 

Glucose can be detected with Fehling s solution, another reaction based on copper reduction. Other reducing substances also interfere with this test. 

The formation of a red precipitate of copper(I) oxide by reduction of Cu(II) is taken as a positive test for an aldehyde Carbohydrates that give positive tests with Benedict s reagent are termed reducing sugars... 

Tea extracts and tea polyphenols inhibit copper- and peroxide-induced oxidation of LDL in vitro (116,123,124). The inhibitory concentration for 50% reduction (IC q) values for inhibition of copper-induced oxidation of LDL by some phenoHc antioxidants are Hsted in Table 7. The IC q for epigaHocatechin gaHate was found to be 0.075 p.mM, which was the most potent of all the phenoHc antioxidants tested (123,124). Similar results have been reported elsewhere (115,116,125,126). 

The elements are obtainable in a state of very high purity but some of their physical properties are nonetheless variable because of their dependence on mechanical history. Their colours (Cu reddish, Ag white and Au yellow) and sheen are so characteristic that the names of the metals are used to describe them. Gold can also be obtained in red, blue and violet colloidal forms by the addition of vtirious reducing agents to very dilute aqueous solutions of gold(III) chloride. A remarkably stable example is the Purple of Cassius , obtained by using SnCla as reductant, which not only provides a sensitive test for Au but is also used to colour glass and ceramics. Colloidal silver and copper are also obtainable but are less stable. 

Oxidation-reduction potential Because of the interest in bacterial corrosion under anaerobic conditions, the oxidation-reduction situation in the soil was suggested as an indication of expected corrosion rates. The work of Starkey and Wight , McVey , and others led to the development and testing of the so-called redox probe. The probe with platinum electrodes and copper sulphate reference cells has been described as difficult to clean. Hence, results are difficult to reproduce. At the present time this procedure does not seem adapted to use in field tests. Of more importance is the fact that the data obtained by the redox method simply indicate anaerobic situations in the soil. Such data would be effective in predicting anaerobic corrosion by sulphate-reducing bacteria, but would fail to give any information regarding other types of corrosion. 

The relatively high cost and lack of domestic supply of noble metals has spurred considerable efforts toward the development of nonnoble metal catalysts for automobile exhaust control. A very large number of base metal oxides and mixtures of oxides have been considered, especially the transition metals, such as copper, chromium, nickel, manganese, cobalt vanadium, and iron. Particularly prominent are the copper chromites, which are mixtures of the oxides of copper and chromium, with various promoters added. These materials are active in the oxidation of CO and hydrocarbons, as well as in the reduction of NO in the presence of CO (55-59). Rare earth oxides, such as lanthanum cobaltate and lanthanum lead manganite with Perovskite structure, have been investigated for CO oxidation, but have not been tested and shown to be sufficiently active under realistic and demanding conditions (60-63). Hopcalities are out-... 

The NO reduction over Cu-Ni-Fe alloys has been studied recently by Lamb and Tollefson. They tested copper wires, stainless steel turnings, and metal alloys from 378 to 500°C, at space velocities of 42,000-54,000 hr-1. The kinetics is found to be first order with respect to hydrogen between 400 and 55,000 ppm, and zero order with respect to NO between 600 and 6800 ppm 104). The activation energies of these reactions are found to be 12.0-18.2 kcal/mole. Hydrogen will reduce both oxygen and NO when they are simultaneously present. CO reduction kinetics were also studied over monel metals by Lunt et al. 43) and by Fedor et al. 105). Lunt speculated that the mechanism begins by oxidant attack on the metal surface... 

The substrates tested alone have substantially different values. Polycarbonate (1/4 inch) structural foam has an of 27.5, modified-polyphenylene oxide (1/4 inch), 84.4, and RIM polyurethane (1/2 inch), 173.3. These values compare with 164.4 for 1/4 inch hardboard and 139.1 for 1/4 inch plywood. A comparison of graphite, nickel, and copper/aciylic coatings on polycarbonate and modified-polyphenylene oxide substrates illustrate a dramatic result. Despite a factor of 3 difference in substrate performance, the Q and Fs values for the coated samples are very similar. The Q for the modified-polyphenylene oxide samples are 0.7 to 0.5 that of the uncoated sample. One would expect a similarity in Fs for the coated sample, but such a reduction in Q is dramatic. Both Q and Fs are determined by the 2 mil surface. 

Sherritt-Cominco A process for extracting copper from chalcopyrite, CuFeS2. The ore is reduced with hydrogen, the iron leached out with sulfuric acid, the residual Cu5FeS4 dissolved in concentrated sulfuric acid, and the copper isolated by electrowinning or hydrogen reduction. Pilot testing was complete in 1976. 

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