[TheMoose]

In a lab experiment, we combined methylcyclohexanol and phosphoric acid in a round bottom flask and heated the contents.  Water and cyclohexene products were distilled out.  The instructions said to let the rxn continue until a certain amount of product was collected or until the formation of dense white fumes.  My question is what is the white fumes?  This comes from Operational Organic Chemistry by John Lehman, Experiment 21.  I'm guessing quite a few people have done this as a google search  of "Acid Catalyzed Dehydration of Methylcyclohexanol" produced many results all appearing to use the same rxn conditions.  Second question is for people who have done this before, what is a good percent yield for this rxn?  The products are constantly being distilled out of solution and using Le Chatlier's principle we know that will drive the rxn to products, so I'm guessing typical yields for this are pretty high.

Thanks for all responses.

EDIT: After talking to a friend of mine, he suggested the fumes could have been gaseous phosphoric acid.  With a lower volume to heat, the mixture temperature would have risen dramatically, possibly up to the bp of the acid around 158 C ( from wiki ).  I should also add that the fumes appeared instantaneously and were accompanied by a popping sound.  They appeared like a fog in that they didn't disperse through the condensing head, instead they just remained in the flask.