A laboratory guide in elementary bacteriology / by William Dodge Frost.

Date:
1903
Catalogue details

Licence: In copyright

Credit: A laboratory guide in elementary bacteriology / by William Dodge Frost. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    EXERCISE 2. PLUGGING FLASKS AND TUBES. General Directions. When the flasks, test-tubes and fer- mentation tubes are thoroughly dry they are to be plugged with cotton. The cotton for this purpose should be non-absorbent and of the best quality, i. e., as free from foreign matter as possible. The plugs should be sufficiently loose to permit the interchange of gases and at the same time tight enough to support the weight of the vessel and its contents, otherwise they are apt to be pulled out in handling the vessels. The cotton should be rolled into a cylin- der of the proper diameter and long enough to extend into the mouth about 2y2 cm. (1 in.) and project sufficiently to protect the lips from dust. The plug should be pushed in straight and not twisted; the surface next to the glass must be perfectly smooth, presenting no creases for the entrance of dust. References. A. 127; II. 44; M. & R. 49; McF. 164; P. 223. Special Directions. Plug all test-tubes, flasks and fermenta- tion tubes in your possession. EXERCISE 3. STERILIZATION OF GLASSWARE. General Directions. The glassware thus prepared is ready for sterilization, which process is accomplished in an apparatus called the hot air sterilizer. This is a sheet iron or copper box with a double wall which permits of rapid heating. The apparatus should be so ar- ranged that a temperature of 150° C. can be quickly reached and readily main- tained. In such a sterilizer all glassware L. to be used for the reception of culture media, such as flasks, test-tubes, Petri dishes, etc., is submitted to a temperature of 140-150° C. for 1 hour, or until the cotton plugs are slightly browned; this change being due to the incipient char- ring of the cotton. The test-tubes are placed erect in square baskets made of galvanized iron wire. When the air in the sterilizer has cooled to about 40° C. the glassware can be taken out and stored ready for use. The Petri dishes are not to be opened until used for culture purposes. References, A. 75 and 127; H. 36; M. & R. 29; McF. 164; P. 223. \ / s Fig. 1. Hot Air Sterilizer, (Muir & Ritchie).