Organic molecules from aqueous solutions absorption

Absorption of Organic Molecules from Aqueous Solutions... 

However, the system CoCl2-Triton X-lOO-decanol-water shows quite different behavior. The tetrahedral complex has its absorption maximum at A = 669 nm in the microemulsion. In addition, a tetrahedral complex is also formed in the organic medium, in pure decanol (Amax = 666 nm), and in pure Triton X-100 (Amax = 673 nm).The intermediate value in the microemulsion suggests that the Co(II) ions in the tetrahedral complex are solvated by both decanol and Triton X-100 molecules. The absorption maximum of the octahedral complex, Amax = 525 nm, is quite different from the aqueous solution value, max = 510 nm. This difference confirms the coordination of Co(II) ions by both Triton X-100 and decanol molecules (see also the NMR results). As the solubility of C0CI2 is non-negligible in both pure decanol and Triton X-100, further work is necessary to analyze more quantitatively this rather complicated system. 

Although the effect of molecular interactions is ordinarily not significant at concentrations below 0.01 M, some exceptions occur among certain large organic ions or molecules. For example, the molar absorptivity at 436 nm for the cation of methylene blue in aqueous solutions is reported to increase by 88% as the dye concentration is increased from 10 to 10" M even below 10 M, strict adherence to Beer s law is not observed. 

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