There is a video 

Return to the Chem113 SYLLABUS
Return to the  Dumas MW PreLab

This method of determining molecular weights is limited to materials which can be vaporized and whose vapors obey the ideal gas law.

The modification you will use in this experiment puts additional restrictions on the materials which can be studied.

For a more detailed view of this experiment see.......... DUMAS MW

Consider the picture on the left. At this point you should have no problem answering the question, " Which is more dense, air or the brown gas flowing out of this cylinder?". But can you answer the question, "Which has the higher Molecular Weight, air or the gas coming out of this cylinder?" If you have to guess, you don't understand the Ideal Gas Law!