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 _b_, are afterward closed.

[Illustration: DR. BUeNTE'S GAS BURETTE]

By a contrary operation, the gas is made to pass from B into the
burette. It is then allowed to cool, and, after the pressure has been
established again, the contraction is measured. If the gas burned is
hydrogen, the contraction multiplied by two-thirds gives the original
volume of the hydrogen gas burned. If the gas burned is oxide of carbon,