A New Type of Gas Burette.

Abstract

Gas burettes reading directly to 0.01 cc., and by estimation to 0.001 cc., are used in certain kinds of apparatus, for example, that of Haldane. A serious limitation of such burettes is that the fine graduation covers only a small fraction of the total volume. In a 10 cc. Haldane's apparatus, the fine graduation usually extends only from 7 to 10 cc. Analysis of a mixture of gas containing more than 30% of a gas to be determined by absorption cannot be made with the apparatus in the usual manner. Nor can samples less than 7 cc. be taken for analysis.

If the fine graduation is extended to the whole of the burette, even with a capacity of only 10 cc., it would have to be more than a meter long. This is, of course, impractical.

In designing a special apparatus for the study of gas equilibria in blood, we have developed a new type of burette which permits reading of volume from 0.1 to 50 cc. or more directly to 0.01 cc. The length of the burette need not exceed 25 cm. Such a burette can, of course, be incorporated into any apparatus.

The principal feature is the division of the total volume into 2 or more portions. The burette shown in the accompanying figure has a capacity of 50 cc. and is divided into 3 arms. Arm A has a capacity of 2 cc., or preferably a little more, and is graduated to 0.01 cc. Arm B consists of ten 2-cc. bulbs, while Arm C consists of three 10-cc. bulbs. These bulbs are conveniently blown out of a 2 mm. capillary tubing. The 3 arms are joined together above the graduations by a 2-mm. capillary tubing.