The principal rapid, non‐digestive methods listed in the literature were surveyed and briefly tested. The diquinolyl procedure was found to be best for copper in the 0 to 10 p.p.m. range. Below I p.p.m. the own colour of the whisky or brandy interfered with the estimation. Colour removal by active carbon altered the copper content.
A simple microdiffusion procedure is described for the determination of acetaldehyde in beer, whereby the acetaldehyde content of the beer sample in the outer chamber of a Conway unit is absorbed in a semicarbazide solution and the optical density of the product is measured at 224 mμ. The estimation is not specific for acetaldehyde, as it in fact determines total volatile carbonyl compounds. A colorimetric estimation is also described.
The compound 3‐methoxy‐2‐nitrosophenol forms a strongly coloured complex with cobalt, which can be extracted from its aqueous solution with organic solvents. The published method of Torii has been investigated and modified. The modified method is suitable for the determination of cobalt in beer in concentrations between 0 and 2 p.p.m. with an accuracy of ±0.02 p.p.m.
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