Cooling an acetanilide mixture with an ice bath has resulted to a heavier amount of acetanilide crystals than cooling the container slowly (setting it aside in the lab). I have gotten different explanations from this. Some say that increasing the cooling rate can include impurities which increases the mass of the crystals. But according to others, decreasing the cooling rate allows the crystal to grow which increases its overall yield.
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$\begingroup$ The experimental results seem to refute one of hypothesis in this case, or at least confirm which of the phenomena is prevalent. $\endgroup$– PoutnikMar 8 at 5:44
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1$\begingroup$ The two cases need not be a contradiction. For example, the first describes a slurry of amorphous solid and small cristallites with solvent adsorbed (occlusion)/incorporated - upon exposure to ambient air, the solvent eventually may evaporate off while the second seeks to use good conditions to seed, and then to grow good crystals. For the later, the two sets of parameters can differ (see e.g., chemistry.stackexchange.com/questions/156251/…) regardless if you aim for crystals easily filtered off, or an XRD analysis. $\endgroup$– ButtonwoodMar 8 at 7:48
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2$\begingroup$ What is the quantitative difference between the yields when comparing both processes ? Is it a couple of percents ? More ? Less? $\endgroup$– MauriceMar 8 at 10:59
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