Determination of impurities in high-purity solvents by neutron activation analysis

Rausch, H.; Sziklai, I. L.; Nazarov, V. M.; Bodon, P.; Erdelyvari, I.; Tóth, Brigitta

doi:10.1007/bf02060355

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…It is well established that liquid solutions almost inevitably contain microscopic solid impurities whose surfaces promote heterogeneous nucleation [48][49][50] and that solid additives can influence the outcome of crystallization processes [13,51,52]. Nucleation centers at the solid surface, such as defects or other sites with high local energy, can create nucleation pathways with lower activation barriers than in homogeneous nucleation.…”

Section: Heterogeneous Nucleationmentioning

confidence: 99%

Homogeneous Organic Crystal Nucleation Rates in Solution from the Perspective of Chemical Reaction Kinetics

Schroeder

2024

Crystals

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It is demonstrated for 11 different combinations of organic solutes and solvents that the supersaturation dependence of homogeneous organic crystal nucleation rates from solution can be predicted from the solubility, bar a single empirical rate constant, when it is assumed that nucleation takes place in reversible aggregates of solvated solutes formed in supersaturated solutions. Reversible solute aggregation represents natural solute density fluctuations that take place in any solute/solvent system. For thermodynamically ideal solutions, the steady state size distribution, and thus the population of reversible aggregates in supersaturated solution, can be predicted quantitatively from the overall solute concentration by a simple mathematical expression. Supersaturation creates an excess of reversible aggregates with sizes exceeding that of the largest aggregate in saturated solution. It is shown that the number of these excess aggregates is proportional to experimental homogeneous nucleation rates, suggesting a rate equation for homogeneous nucleation that has only one empirical parameter, namely, a rate constant specific to the solute/solvent combination. This rate constant can be determined from standard nucleation rate data. The system-specificity of homogeneous nucleation rates thus appears to be encoded solely in a rate constant for the transformation of the large excess aggregates into crystal nuclei. The driving force for triggering nucleation events in these aggregates is likely the extremely high local supersaturation, which provides the conditions for spatiotemporally aligned bond-breaking (e.g., de-solvation) and bond-forming (e.g., solute–solute bonding) events that create stable crystal nuclei. The possible influence of heterogeneous nucleation by solid impurities is considered.

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Section: Heterogeneous Nucleationmentioning

confidence: 99%

Homogeneous Organic Crystal Nucleation Rates in Solution from the Perspective of Chemical Reaction Kinetics

Schroeder

2024

Crystals

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“…Figure 3-2 shows the schematic diagram of the quartz double sub-boiling distillation unit, used for the purification of H2S04 at the NBS laboratories since 1976. Recent developments in the purification of chemicals, relevant for trace element analysis, are the use of preparative HPLC for organic solvents [106], improvements in the commercially available water purification systems down to < 0.5 pg.kg-' total dissolved metals [24] and the interest in anionic impurities in mineral acids [95]. He discusses a modification by Oehme and Lund [102], of the nowadays widely used Millipore Milli-Q system for water purification.…”

Section: Contaminationmentioning

confidence: 99%