“Disappearing Polymorphs”, 1995 (; backlinks; similar):
When a compound exhibits polymorphism—the existence of more than one crystal structure—it may be important to obtain a particular polymorph under controlled and reproducible conditions. However, this is not always easy to achieve.
Tales of difficulties in obtaining crystals of a particular known form or in reproducing results from another laboratory (or even from one’s own!) abound. Indeed, there are cases where it was difficult to obtain a given polymorphic form even though this had previously been obtained routinely over long time periods.
Several monographs contain explicit or passing references to these problems, but much of this lore has gone undocumented, especially in the last 30 years or so. In this Account, we present and discuss old and new examples.
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