The Concept of Coredox Reaction

Eleven sets of organic and inorganic coloured reduction-oxidation (coredox) reactions (organic and inorganic chemical reactions that can show change in colour brightness after undergo redox reaction) were used during these research findings. All were carried out under suitable condition in order to see if the compounds that exist as coloured compounds before reaction, after reaction or both will become brighter or darker when undergo reduction or oxidation respectively. Six sets of this reaction type which include both organic and inorganic species showed special results. In which, all the targeted species gained electrons, their oxidation number decreased in positive direction and colour of species became brighter after reaction by increased in colour brightness. While in last five sets, which also include both organic and inorganic species showed their own results in which all the targeted species donated electrons, their oxidation number increased in positive direction, colour of species became darker after reaction by decreased in colour brightness. Series and repeated number of observations (more than 20 times) were made before recording any changed in colour brightness. Therefore, for all pure form of chemical species that can undergo any one of the coloured reduction-oxidation (coredox) reaction, brightness formation of the product after reaction implies reduction while darkness, oxidation.

A review of the current knowledge of red wine colour.

<p><span lang="EN-GB">Anthocyanins are the main compounds present in young red wines, being responsible for their intense red colour. <span>These pigments are mainly located in grape skins and their extractability during winemaking depends on many factors, such as their concentration in vacuoles and interaction with the cell-wall polysaccharides, affecting their stability and concentration in the must.</span> The red colour of anthocyanins at wine pH is explained by the stabilization of the flavylium cation form that displays a red colour; otherwise at this pH the hemiketal colourless is the dominant form, bleaching the wine. <span>Besides the contribution of free anthocyanins, a phenomenon called copigmentation influences the colour of young red wines.</span> Copigmentation can be defined as a</span><span lang="EN-GB"> series of stabilization mechanisms involving van der Walls interactions that occur naturally in red wines and that can explain this unanticipated colour behaviour. </span><span lang="EN-GB">Copigmentation</span><span lang="EN-GB"> is also pointed as the first interaction between anthocyanins and other wine components leading after that to the formation of new coloured compounds </span><span lang="EN-GB">during </span><span lang="EN-GB">red wine </span><span lang="EN-GB">ageing</span><span lang="EN-GB">. Some of these pigments have already been identified and characterized but <span>many are</span> still undiscovered.</span><span lang="EN-GB"> The detection and structural characterization of new pigments, and the knowledge of their chemical formation pathways are crucial <span>to</span> better <span>understand</span> the evolution of the colour of red wine during ageing.</span></p>

Osmium assay in fixatives and stained rat tissues by means of acid and o,o′-dihydroxo substituted monoazo dyes and some flavonoids

New simple, rapid and accurate spectrophotometric techniques for osmium assays in fixatives and stained tissues have been elaborated using acid (Tropaeolin O, Tropaeolin OOO-I, Tropaeolin OOO-II, Orange G), o,o′-dihydroxo substituted azo dyes (Eriochrome Blue Black R, Acid Chrome Dark-Blue, Eriochrome Black T) and flavonoids (morin, quercetin, luteolin). Methods are based on sensitive osmium(IV) reactions with reagents and the formation of stable coloured compounds. Tolerance ratios of main matrix components of histological specimens during Os(IV) spectrophotometric determination with reagents has been established. Results of osmium determination in fixatives and fixed tissues, obtained by means of different reagents, appeared to be sufficiently similar, although effects of matrix components differ. The accuracy of spectrophotometric osmium assay in fixatives with azo dyes has been confirmed with voltammetric investigations. Results obtained from osmium uptake by rat gum tissues are valuable for clinical testing of dental drugs, indicating the influence of drug treatment on the gums.