Scientific American Supplement, No. 360, November 25, 1882

by Various

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.

If not enough absorbing liquid has entered, there may be sucked into the burette, by the process described above, a new quantity of liquid. The reaction finished, the graduated cylinder is put in communication with the funnel by turning the cock, a. The water is allowed to run from the funnel, and the latter is filled again with water up to the mark. The gas is then again under the same pressure as at the beginning.

After the level has become constant, the quantity of gas remaining is measured. The contraction that has taken place gives, in hundredths of the total volume, the volume of the gas absorbed.

When it is desired to make an analysis of smoke due to combustion, caustic potassa is first sucked into the burette. After complete absorption, and after putting the gas at the same pressure, the diminution gives the volume of carbonic acid.

To determine the oxygen in the remaining gas, a portion of the caustic potash is allowed to flow out, and an aqueous solution of pyrogallic acid and potash is allowed to enter. The presence of oxygen is revealed by the color of the liquid, which becomes darker.

The gas is then agitated with the absorbing liquid until, upon opening the cock, a, the liquid remains in the capillary tube, that is to say, until no more water runs from the funnel into the burette. To make a quantitative analysis of the carbon contained in gas, the pyrogallate of potash must be entirely removed from the burette. To do this, the liquid is sucked out by means of the flask, S, until there remain only a few drops; then the cock, a, is opened and water is allowed to flow from the funnel along the sides of the burette. Then a is closed, and the washing water is sucked in the same manner. By repeating this manipulation several times, the absorbing liquid is completely removed. The acid solution of chloride of copper is then allowed to enter.

As the absorbing liquids adhere to the glass, it is better, before noting the level, to replace these liquids by water. The cocks, a and b, are opened, and water is allowed to enter from the funnel, the absorbing liquid being made to flow at the same time through the cock, b.

When an acid solution of chloride of copper is employed, dilute hydrochloric acid is used instead of water.

Fig. 2 shows the arrangement of the apparatus for the quantitative analysis of oxide of carbon and hydrogen by combustion. The gas in the burette is first mixed with atmospheric air, by allowing the liquid to flow through b, and causing air to enter through the axial aperture of the three way cock, a, after cutting off communication at v. Then, as shown in the figure, the burette is connected with the tube, B, which is filled with water up to the narrow curved part, and the interior of the burette is made to communicate with the combustion tube, v, by turning the cock, a. The combustion tube is heated by means of a Bunsen burner or alcohol lamp, L. It is necessary to proceed, so that all the water shall be driven from the cock and the capillary tube, and that it shall be sent into the burette. The combustion is effected by causing the mixture of gas to pass from the burette into the tube, B, through the tube, v, heated to redness, into which there passes a palladium wire. Water is allowed to flow through the point of the tube, B, while from the flask, F, it enters through the bottom into the burette, so as to drive out the gas. The water is allowed to rise into the burette as far as the cock, and the cocks, b and b¹, are afterward closed.