To fill the burette with gas, the three-way cock, _a_, is so placed that the axial aperture shall be in communication with the graduated part, A, of the burette. After this, water is poured into the funnel, t, and the burette is put in communication with the gas reservoir by means of a rubber tube. The lower point of the burette is put in communication with a rubber pump, V (Fig. 2), on an aspirator (the cock, _b_, being left open), and the gas is sucked in until all the air that was in the apparatus has been expelled from it. The cocks, _a_ and _b_, are turned 90 degrees. The water in the funnel prevents the gases communicating with the top. The point of the three-way cock is afterward closed with a rubber tube and glass rod. If the gas happens to be in the reservoir of an aspirator, it is made to pass into the apparatus in the following manner: The burette is completely filled with water, and the point of the three-way cock is put in communication with a reservoir. If the gas is under pressure, a portion of it is allowed to escape through the capillary tube into the water in the funnel, by turning the cock, _a_, properly, and thus all the water in the conduit is entirely expelled. Afterward _a_ is turned 180°, and the lower cock, _b_, is opened. While the water is flowing through _b_, the burette becomes filled with gas. _Mode of Measuring the Gases and Absorption_.--The tube that communicates with the vessel, F, is put in communication, after the latter has been completely filled with water, with the point of the cock, _b_ (Fig. 2). Then the latter is opened, as is also the pinch cock on the rubber tubing, and water is allowed to enter the burette through the bottom until the level is at the zero of the graduation. There are then 100 cubic centimeters in the burette. The superfluous gas has escaped through the cock, _a_, and passed through the water in the funnel. The cock, _a_, is afterward closed by turning it 90°. To cause the absorbing liquid to pass into the burette, the water in the graduated cylinder is made to flow by connecting the rubber tube, s, of the bottle, S, with the point of the burette. The cock is opened, and suction is effected with the mouth of the tube, r. When the water has flowed out to nearly the last drop, _b_ is closed and the suction bottle is removed. The absorbing liquid (caustic potassa or pyrogallate of potassa) is poured into a porcelain capsule, P, and the point of the burette is dipped into the liquid. If the cock, _b_, be opened, the absorbing liquid will be sucked into the burette. In order to hasten the absorption, the cock, _b_, is closed, and the burette is shaken horizontally, the aperture of the funnel being closed by the hand during the operation.