volumescope

from The Century Dictionary.

• noun A graduated glass tube for demonstrating the difference in volume of the components of a compound, especially when they are set free by chemical action.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) An instrument consisting essentially of a glass tube provided with a graduated scale, for exhibiting to the eye the changes of volume of a gas or gaseous mixture resulting from chemical action, etc.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An instrument consisting of a glass tube with a graduated scale that shows the changes in volume of a gas or gaseous mixture.