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The Relation between the Rate of Formation of the Chromium Complexes of a Dye and its Value in the Metachrome Process
Author(s) -
RACE E.
Publication year - 1950
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1950.tb02631.x
Subject(s) - chromium , chemistry , molecule , salt (chemistry) , chelation , inorganic chemistry , photochemistry , polymer chemistry , organic chemistry
A study has been made of the rates of formation and the nature of the chromium complexes of selected dyes in order to ascertain whether or not a relationship exists between the rate of complex formation and the suitability of a dye for application by the metachrome process. The results indicate that, in the case of azosalicylic acid compounds containing a sulpho group, the dyes are unsuitable for use in the metachrome process probably because of co–ordination of chromium with the sulpho group instead of, or as well as, chelation of chromium with the salicylic acid group. The examination of the rates of formation of the chromium complexes of a series of 00′‐dihydroxyazo compounds of diminishing value as metachrome dyes has revealed that the greater the rate of chromium‐dye complex formation the more suitable is the dye for application by the metachrome process. The results suggest that both substantivity and rate of complex formation play important rdles in the determination of the value of a metachrome dye, and that both of these factors should be as high as possible, consistent with solubility. The experimental data demonstrate that, in the case of the series of 00′‐dihydroxyazo dyes employed, the final product of reaction of dye and chromium salt is the primary complex, in which one molecule of dye is associated with one atom of chromium. This product is formed via the chromium salt of the dye and a complex in which three molecules of the dye are associated with one atom of chromium. The analyses have not disclosed whether conversion of the 3: 1 complex occurs directly to the 1: 1 complex or whether the 2: 1 acidic complex is formed as an intermediate product.