| 1. |
- Cerreta, M.K., et al.
(författare)
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The structure of aqueous solutions of some dihydrogen orthophosphates by laser Raman spectroscopy
- 1987
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 84:4, s. 577-588
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Tidskriftsartikel (refereegranskat)abstract
- Powdered crystals and pure, aqueous solutions of ammonium, sodium, and potassium dihydrogen orthophosphates in concentrations ranging from 0.01M to supersaturated were investigated at 30°C using laser Raman spectroscopy between 700 and 1350 cm-1. With increasing solute concentration, the peak position of the 875 cm-1 P-(OH)2 symmetric strech band increased. Extreme asymmetry in the 1075 cm-1 P=O2 symmetric stretch band developed to lower energy. The integrated intensity ratio of the 875 cm-1 band to the 1075 cm-1 band envelope remained constant. These observations are consistent with anion-anion association via hydrogen bonds. Deconvolution of the spectral bands showed only 40% and 20% of the phosphates exist as monomers in saturated potassium and ammonium solutions, respectively, and that anion association does not cease at the dimer. The spectra provided no evidence of quasi-crystalline entities in solution. The necessary breaking and reforming of hydrogen bonds during the growth process can explain rapid z-direction growth, growth activation energy, and the rate-limiting surface growth mechanism.
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| 2. |
- Larson, M.A., et al.
(författare)
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Growth rate dispersion in MSMPR crystallizers
- 1985
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Ingår i: AIChE Journal. - : Wiley. - 0001-1541 .- 1547-5905. ; 31:1, s. 90-94
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Tidskriftsartikel (refereegranskat)abstract
- A model is presented which relates the crystal size distribution (CSD) from a mixed-suspension, mixed-product-removal (MSMPR) crystallizer to the distribution of growth rates. This model is based on the assumption that individual contact nuclei have some inherent growth rate which remains constant, but the growth rate may vary from crystal to crystal. The crystal size distribution can be calculated from prior knowledge of the growth rate distribution. A limited knowledge of only the coefficient of variation and the mean growth rate permits an approximation of the expected crystal size distribution. Conversely, estimates of the mean and variance of the growth rate distribution can be determined from the moments of the CSD from an MSMPR crystallizer
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| 3. |
- McMahon, Paula M., et al.
(författare)
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A constant-temperature Raman cell for the study of supersaturated aqueous solutions
- 1986
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 40:2, s. 282-283
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Tidskriftsartikel (refereegranskat)abstract
- In order that the phenomena of crystal nucleation and growth from solution can be fully understood, the current knowledge of supersaturated solution structure must be extended. Previous studies on Raman spectroscopy of aqueous metal nitrate solutions indicated the presence of solvated ions, solvent separated ion pairs, contact ion pairs, and ion agglomerates as a function of concentration. Unfortunately, the concentration range of these studies did not include supersaturated solutions. It is the purpose of this work to describe an experimental technique which allows the study of supersaturated solutions.
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