A text-book of general bacteriology / by Edwin O. Jordan.

  • Edwin O. Jordan
Date:
1931
Catalogue details

Licence: In copyright

Credit: A text-book of general bacteriology / by Edwin O. Jordan. Source: Wellcome Collection.

    41/830 page 39
    THE FERMENTATION TUBE NaOH solution and the mouth of the tube closed tightly with the thumb. The gas is tilted back and forth between the bulb and the closed arm several times and finally allowed to collect in the closed arm. When the thumb is released the fluid rises in the arm, due to the fact that the sodium hydrate has absorbed the carbon dioxide; the residual gas, which is usually chiefly hydrogen, can then Fig. 6.—Frost’s chart for measuring gas in the fermentation tests (Heine- mann’s “Laboratory Guide”). be measured. The ratio of hydrogen to carbon dioxide or the gas for¬ mula of an organism may be stated, for example, as follows: H2 : C02 : : 30 : 15 : : 2 : 1. It is evident that results obtained in this manner can never be precise. The solubility of carbon dioxide leads to the retention in the medium of a varying percentage of this gas dependent on the acidity of the medium, the opportunities for loss into the atmos¬ phere, and other factors. It has been shown, especially by Keyes,1 that more uniform and comparable results can be obtained by using bulbs sealed after the exhaustion of the air. A modified form (Figs. 1 Keyes: Jour. Med. Research, 1909, 21, p. 69.
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