The effect of additives on the corrosion of tin in alkaline solution

In order to study the effect of potassium chloride, sodium nitrite and sodium chloride on the corrosion of tin, in solutions of sodium hydroxide, the method of galvanic couples has been used. Cathodic and anodic potentials and the limiting current densities of the tin-platinum couple have been measured in order to determine the corrosion rate and type of control exerted by additives. The results indicate that the nature and concentration of additives exert an influence on the dissolution process of tin. Weight loss experiments have been also performed; data obtained are compared with electrochemical results. The significance of such additives on the corrosion of tin is discussed.     

Chemical and sensory characterization of oxidative behavior in different wines

In wine making, the redox phenomena are responsible for profound changes in the wine’s chemical composition. Twenty wines set has been selected trying to cover a wide range of behaviors against to oxidation–reduction phenomenon. Free SO₂ level was adjusted to the maximum level found to avoid its influence from the wine oxidative trend. Samples of this set of wines were submitted to extreme conditions during 1 month. Samples were taken in different days for sensorial and chemical analysis. It is proved that red wines oxidation velocity is much higher than white wines. Aldehydes were quantified by gas chromatography–negative ion mass spectrometry (GC–NCI–MS) using a previous derivatization procedure. In conclusion, it can be said that the speed at which the sensory characteristics of wine changes are loosely related to the production of relevant odor active aldehydes, particularly to levels of methional and phenylacetaldehyde. In general, red wines produce those aldehydes during oxidation at a much higher speed than white wines, which is in agreement with the observed changes in sensory properties. However, it was not possible to find good correlations between sensory changes and aldehyde production within the red or white subsets.