. Laboratory work in bacteriology. Bacteriology. / FILTRATION OF BACTERIAL LIQUIDS. 471 The mouth of the sterile bougie is now flamed and connected with the sterile glass tube which passes ^through the rubber stopper. A glass globe similar to that of Martin can be used in place of an Erlenmeyer flask to receive the filtrate (Fig. 68 B). The cylinder is now inverted and connected with the receiver (Fig. 66 e). Ordinary liquids can be filtered by the aid of a Chapman aspira- tor. If the liquid under these conditions filters slowly, the neck of the globe (Fig. 66 h) should be connected with a tan

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. Laboratory work in bacteriology. Bacteriology. / FILTRATION OF BACTERIAL LIQUIDS. 471 The mouth of the sterile bougie is now flamed and connected with the sterile glass tube which passes ^through the rubber stopper. A glass globe similar to that of Martin can be used in place of an Erlenmeyer flask to receive the filtrate (Fig. 68 B). The cylinder is now inverted and connected with the receiver (Fig. 66 e). Ordinary liquids can be filtered by the aid of a Chapman aspira- tor. If the liquid under these conditions filters slowly, the neck of the globe (Fig. 66 h) should be connected with a tank containing compressed air. When pressure is applied care must be taken to prevent the stopper or the glass tube ftom being blown out of place. The end of the glass tube after it has been slipped through the rubber stopper is softened in the flame and then fianged by means of a piece of charcoal or a nail. The stopper, when inserted, should be wired securely in place. A brass ring (h), placed on the upper side of the stop- per, will prevent it from being cut by the wires. The compressed air is contained in ' a small steel cylinder such as is used by physicians for atomizing purposes. A cheap substitute can be made by con- necting a domestic, hot-water tank with a pressure gauge and a bicycle pump.. Fig. 68. A Berkefeld filter showing connections; a—Rubber disc; *—Iron plate; 5—Globe receiver (F. G. N.). The Berkefeld filter can be attached to the glass cylinder in a somewhat simi- lar manner. An iron plate (Fig. 68 6) 5-6 mm. thick and 7 cm. in diameter is provided with a central opening (1.2 cm. diameter) just sufficient to allow the nozzle of the filter to pass through. A rubber ring (Fig. 68 a), 7 cm. in diameter and 2 mm. thick, with a central opening 3 cm. in diameter, is placed between the glass flange and the iron plate. The whole is then clamped securely. In place of the Erlenmeyer vacuum flask (Fig. 66 e), a glass globe, like that shown in Fig. 68 B can be emplo

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