Methods of air analysis / by J.S. Haldane.

  • John Scott Haldane
Date:
1920
Catalogue details

Licence: In copyright

Credit: Methods of air analysis / by J.S. Haldane. Source: Wellcome Collection.

    39/162 (page 23)
    The sampling tube is connected with the mercury reser¬ voir, any air-bubbles being driven out through the free limb of the lower three-way tap. The burette is also connected with one end of the sampling tube by a piece of glass tubing of 2 mm. bore, and bent as shown in the figure. The gas in the burette is then expelled through the free limb of the three-way tap on the upper end of the sampling tube, and mercury is driven over so as to fill the connections up to this tap. Any mercury which escapes can be caught in a small test-tube hung from the barrel of the tap by a wire. The tap on the sampling tube is then completely closed, and the levelling- tube depressed, so that any leakage in the connections, or the presence of any air-bubble, can be detected at once. An air-bubble sometimes sticks at the rubber joint between the connecting tube and sampling tube. To expel this the easiest plan may be to pinch one side of the rubber so as to allow a channel of escape for the bubble. Soft, black rubber should therefore be used in making the joint. When everything is ready the level¬ ling-tube is lowered and the taps opened so that a sample is sucked into the burette. The pressure inside the burette can then be adjusted to normal by raising or lowering the reservoir R, or the levelling-tube. If the sampling tube has only plain taps, the glass tubing above the tap must be filled with mercury b}^ means of a fine glass pipette before the sampling tube is joined to the connecting tube. The air is then expelled from the latter after pinching one side of the rubber joint so as to open a channel. The free end of the lower