Air-pump, Bunsen’s Water. (See figure on page 53.)
This consists of a wide glass tube, a, into which another tube, b, b′, b′′, passes air-tight. c is an india-rubber tube connecting a with the water supply, d is a clamp to stop the flow of water through c. e is another clamp to regulate the flow, f is a reservoir to prevent any water which may accidentally come over from getting into j. g is a plug to let out any water from f. h is a screw for connecting a air-tight to a piece of tubing, which should pass 32 feet, if possible, below the level of a. i is a piece of strong india-rubber tubing to connect the pump with the vessel to be exhausted. The water rushes in at c and down h, carrying bubbles of air with it till the exhaustion is complete. The figure illustrates a common application of this pump to the rapid filtration of liquids which ordinarily pass through paper with difficulty. a is represented as being about half full of water. k is a funnel fixed air-tight in the india-rubber stopper of the bell-jar j. l is a small cone of platinum foil to prevent the paper filter which fits into it from being broken. m is a plate of ground glass, n is a beaker to receive the filtrate.
Bunsen’s water-air-pump.
Air-pump, Sprengel’s. This apparatus depends on the principle of converting the space to be exhausted into a torricellian vacuum.
In the subjoined figure, c, d is a glass tube longer than a barometer, open at both ends, and connected by means of india-rubber tubing with a funnel, A, filled with mercury and supported by a stand. Mercury is allowed to fall in this tube at a rate regulated by a clamp at C; the lower end of the tube, c, d, fits in the flask B, which has a spout at the side a little higher than the lower end of c, d; the upper part has a branch at x to which a receiver R can be tightly fixed. When the clamp at C is opened, the first portions of mercury which run out close the tube and prevent air from entering below. As the mercury is allowed to run down the exhaustion begins, and the whole length of the tube from x to d is fitted with cylinders of air and mercury, having a downward motion. Air and mercury escape through the spout of the bulb B, which is above the basin H, where the mercury is collected. It is poured back from time to time into the funnel A, to be repassed through the tube until the exhaustion is complete.
Sprengel’s air-pump.
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