i wil be doing an experiment to determine the empirical formula of magnesium oxide???

Question

why is it important not to let any white fumes escape from the crucible?

Answer 1

Because inhalation of magnesium oxide fumes can cause metal fume fever. It is illness caused primarily by exposure to fumes from zinc oxide (ZnO) or magnesium oxide (MgO), often through breathing fumes created by heating or welding certain metals, such as galvanized steel. The symptoms are nonspecific but are generally flu like including: Fever, chills, nausea, headache, fatigue, muscle aches, and joint pains. A sweet or metallic taste in the mouth which distorts the taste of food and cigarettes is also normally reported along with a dry or irritated throat which may lead to hoarseness. Symptoms may also include a burning sensation in the body, shock, no urine output, collapse, convulsions, shortness of breath, yellow eyes or yellow skin, rash, vomiting, watery or bloody diarrhea or low blood pressure, which require prompt medical attention.

Answer 2

Although you don't want to be breathing it, the reason here is if some of the white fume escapes, you will get a lower weight of magnesium oxide produced for your experiment.

I am presuming you are placing a sample of Mg into a weighed crucible, reweighing, then burning it and reweighing again to find wt increase due to the oxygen that is combined.

If some of the material is lost as fume it would appear as if less oxygen combined with the Mg than was actually the case and you will recieve less of a grade than should actually be the case!