DALTON'S LAW OF PARTIAL PRESSURES Submitled by: F. R. Dutton, Michigan State University Checked by: Julian R. Rraudou, Traveling Science Teacher Progran~ PREPARATION
Obtain a 500-ml or larger filter flask with a one-holc stopper to fit. Insert in the stopper a piece of glass tubing which has been sealed a t one end and is such length that i t will reach nearly to the bottom of the flask and leave a few inches protruding through the top of the stopper. Provide a number of glass ampoules filled with ether or other volatile liquid. For construction and filling of ampoules see remarks below. Place the stem of an ether ampoule into the open end of the glass tube and slip the flask over the assembly. Adjust the glass tube so that it forms a reasonably snug fit with the ampoule against the bottom of the flask. Be careful not to break the ampoule prematurely. Bend a piece of glass tubing to make a U-shaped manometer and attach with rubbrr tubing to the sidearm of the flask. Fill the manometer to an appropriate level with mercury.
A
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8 C
DEMONSTRATION
We have a closed system with the pressure inside the system essentially equal to the atmospheric pressure. Strike the closed end of the glass tube sharply breaking the ampoule. The vapor pressure of the ether is now added to the pressure of the air in the flask; the difference between the new pressure in the flask and the atmospheric pressure can be observed on the mnnometer. REMARKS
Make the ether ampoule from soft glass tubing by drawing out a small thick-wallrd hulb (Fig. A). Seal off one end of the tube, rotate i t in the flame until soft, and blow a large thin-walled hulb (Fig. R). A number of ampoules may be filled a t one time as follows: place them with the open-ended stem down in a small beaker eontaiuing a little ether (Fig. C). Place a few drops of ether over the tops of the bulbs; this will cool them sufficiently to draw some of the liquid up into the bulbs. Quickly remove and invert the tubes; boil off the ether by gentle warming. Now place the ampoules once again in the beaker, stem down, and cool; a sufficientquantity of liquid ether will be drawn up. Seal off the ends of the fine capillaries in the flame and store the ampoules until needed for use. CAUTION: Ethw is hiqhly inflammable. Journol of Chemical Education
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Auouat 1961
