A new type all-glass osmometer of very simple construction using a sintered glass cylinder as rigid support for de-nitrated collodion membrane is described. The solvent is put inside the osmotic cell and the solution outside. Not more than 10 ml of solution is needed for a determination, while the amount of solvent used is extremely small. No special technique is required for the manipulation of the osmometer. It is especially suited for the osmometric studies with mixed solvents, for very viscous solutions and for measurements at several temperatures.