Variable stoichiometry phenomenon

U02(N03)2 TBP complexes and evaluating the individual interfacial resistances. Likewise, Chaudry et al (35) determined the influence of experimental variables, such as the effect of the nitric acid concentration in the feed solution, the TBP concentration in the kerosene membrane, the stripping agent (sodium nitrate, ammonium carbonate) concentration, and the temperature on the uranyl flux. They elucidated the mechanism of uranium transport and the stoichiometry of the transported species. A novel phenomenon, the so-called solubility mechanism was experimentally observed and theoretically explained (36) for uranium transport from a feed solution of 0.01 M uranium in nitric acid at pH 0.7-1.5 through a liquid membrane of 0-100 % of DEHPA in the hydrocarbon solvent Shellsol 2046... 

Even though crystal forms have been and are the subject of intense investigations, polymorphism as a phenomenon still represents a substantial scientific challenge. Indeed it is hard to predict whether a given molecule will crystallize in one or several crystal forms, whether it will form solvates with different stoichiometries or will ever be happy to link up with other molecules and form stable co-crystals. Such variability and unpredictability have been taken by some scientists as an intrinsic drawback of being able to construct desired crystal structures (and obtain relevant properties) from a purposeful choice of the molecular components, which is the paradigm of molecular crystal engineering [15-19]. 

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