The determination of oxygen in copper

The solubility of oxygen in copper is extremely high and it is markedly dependent on pressure and temperature. The following equations for this relationship are quoted by Fromm and Gebhardt (48)  

The hydrogen reduction process meets a much higher analytical standard, and even today is still regarded as a recognized analytical method (51)(52)(53). 

A few other chemical methods will merely be mentioned and not dealt with in detail, because in practice they were never used on a widespread scale reaction with sulphur and sulphur chlorides (24)(54)(55) and spectrochemi-cal analysis (56)(84). 

The outlook is different for the direct electrochemical determination of oxygen in the copper melt using a zirconium oxide sensor stabilized with calcium oxide (57)(80)(81)(85). This method is used to an ever-increasing extent. 

Reducing fusion has become the preferred method for the analysis of solid samples it was used initially in vacuo (58-63), but later on it was increasingly used under carrier gas (64). Both variants are used in a very great diversity of methods of determining the reaction gases. 

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Table VII-3 Variants in the determination of oxygen in copper by inert gas fusion...

For the determination of oxygen in copper, Dahlmann and Fassel (87) use an auxiliary bath of 80 % platinum and 20 % tin in a 3 to 1 bath to sample ratio the reaction temperature is 1725 to 1775 C. The final concentration of copper in the bath should not exceed 10 %. However this procedure must be regarded as completely obsolete it has, in any case, only been used for the determination of fairly high oxygen concentrations. 

Several variants of vacuum fusion are also available for the determination of oxygen in copper. The parameters used in european joint research work (61)(70) are given in Table VII-4. 

It is known (62) that, in the determination of oxygen in copper by both inert gas and vacuum fusion, carbon monoxide is not the only oxygen containing reaction product formed carbon dioxide is also formed to some extent. 

Table VII-5 Analyses carried out to test the determination of oxygen in copper alloys...

Hydrogen reduction is probably only suitable for the determination of oxygen in copper alloys in special cases. It is limited to alloys containing no alloying components or impurities which form oxides that cannot be reduced with hydrogen. Initial work in this field has been carried out by Hofmann and Schneider (93), who were able to analyse lead bronzes and tin bronzes successfully. 

For the determination of oxygen in copper, triton, helium-3 and helium-4... 

F is separated by steam distillation of fluorosilicic acid followed by precipitation of lead chlorofluoride. For helium-3 activation (effective incident energy = 15-18 MeV) no extraction of polonium is required. The results obtained for industrial lead were (0.99 + 0.21) /ig/g (n = 8) for He activation and (0.79 + 0.36) ng/g (n = 8) for He activation. The standard deviations of resp. 21 and 45 % compared to the 10 % obtained when roughly the same analytical technique was applied to the determination of oxygen in copper (213)(245), indicate a less homogeneous distribution of the oxygen in lead. The variance for the He results is significantly... 

In principle, the determination of oxygen in alloys of this type can be carried out in the same way as in unalloyed copper. No interfering side-effects have been observed. However, the vaporization of metals which takes place produces considerable contamination of the apparatus, which requires tedious cleaning processes after each analysis. 

Basically, the same limitations as for the determination of oxygen in aluminium or copper alloys apply to this analysis ... 

The solubility of tritium in copper and gold at high pressures in the temperature interval 473 K-700 K has been determined . Gold annealed at 1273 K in air exhibited much higher solubiUty than samples annealed at 873 K. This effect has been explained by assuming that tritium has been trapped by oxygen which diffused into the sample... 

A DME has also been used for the amperometric determination of oxygen in river water and effluent samples. This involves the application of a constant potential of —1.5V versus the SCE. This approach has been found to be useful in eliminating interferences from cyanide and sulfide, as well as correcting for contributions from metal ions, such as iron, copper, zinc, and nickel. The method can be reliably used for oxygen determination when present within the concentration range of 0-15 mg 1 . ... 

Applications of Radioactive Kryptonates [32], 92J. 94]-[96]. The determination of oxygen is performed by surface oxidation of copper or pyro-graphite kryptonate, at elevated temperature, resulting in destruction of the surface layer and release of Kt proportional to the oxygen mass. Detection limits are at the 10 ng/m level. Ozone oxidizes copper kryptonate at temperatures below 100 °C. whereas reaction with oxygen starts well above 200 °C, so this detector can detect Ox and O2 differentially. Determination of ozone in air is feasible over a concentration range of 10 - 10 g/m with hydroquinone kryptonate ... 

Neither copper nor nickel powder electrodes are sensitive to the presence of oxygen in the system. In a similar way as for the nickel electrode, we determined the normal potential of a copper powder electrode using deactivated copper powder, that is to say, a powder deprived of places of higher state of energy on its surface. Such a powder is, for example, the one obtained by means of electrolysis. 

In the above example, the concentration of copper remains constant (pure copper) so that the reaction rate could be expected to depend on the partial pressure of oxygen in the atmosphere ( Po2)- This would be a first order reaction, but experimental determination of the dependence of the rate on Po2 shows that the rate is approximately proportional to Pq7 implying a fractional order. 

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