Trying to ascertain why certain English words are spelled the way they are can be a very absorbing endeavor. It often feels downright illogical. While the bee pictured to the right is hanging on pretty tight, the (second) B in absorb drops out of sight when the word is expanded (as absorbent substances are wont to do) to absorption. We found 27 examples of Absorbtion in OhioLINK, and 715 in WorldCat. But you should note that not all of those are typos. Some bib records are using the correct spelling in a foreign language (for example, German). Given that this one is really more of a misspelling than an accidental typo, it seems likely that your own database may have absorbed a few of these as well. Watch your B's and P's today and clean up your catalog better than a Bounty (?) paper towel.
("Absorbed in the feast: this bee was completely unaware or perhaps uninterested in my camera lens which was really very close to it!" Photo by Crispin Semmens, 31 May 2008, from Wikimedia Commons.)