Measurements have been made of the nitrogen pressure ratio across a connecting stage as a function of the nitrogen exposure on the high-pressure side. The stage consisted of a titanium evaporator in a spherical glass bulb (8-cm diameter) which was connected to two glass ultra-high vacuum systems via short axially aligned tubes. When an unobstructed straight line path was allowed between the two systems, at least 99% of the transmitted gas was the direct “streaming” component which did not encounter the titanium surface. For the particular design reported here, the resulting pressure ratio was 3.3×104. When the streaming path was obstructed, pressure ratios as high as 3×107 were measured. Saturation of the chemisorption on the evaporated titanium occurred at ∼8×1014 molecules per cm2 of macroscopic area. A single evaporator containing 0.12 g of titanium was able to deposit more than 300 films. Expressions are given from which the performance of other stages of similar design but of different dimensions can be estimated.