. A laboratory guide in bacteriology, for the use of students, teachers, and practitioners. e bottomshelf should always be covered with a piece of asbes-tos, to prevent heating the apparatus too temperature is maintained at 160° or more for onehour. The flame enters a hole provided at .the bottomof the box. Care should be taken to avoid the possi-bility of the flame becoming liuninous, otherwise theglassware will be covered with soot. Culture media and all substances liable to be in-jured by heat of 160° C. or over must be sterilized bythe application of moist heat. Experience has
. A laboratory guide in bacteriology, for the use of students, teachers, and practitioners. e bottomshelf should always be covered with a piece of asbes-tos, to prevent heating the apparatus too temperature is maintained at 160° or more for onehour. The flame enters a hole provided at .the bottomof the box. Care should be taken to avoid the possi-bility of the flame becoming liuninous, otherwise theglassware will be covered with soot. Culture media and all substances liable to be in-jured by heat of 160° C. or over must be sterilized bythe application of moist heat. Experience has taughtthat hot steam has greater germicidal powers than airof the same temperature. Hot steam, therefore, is themost common means of sterilizing culture media. Fig. 4Kochs Hot-Air Sterilizer 12 LABORATORY GUIDE IN BACTERIOLOGY Steam is applied in two ways. The first method isthat of exposing media to steam of 100° C. for 20 min-utes. This is done in an apparatus generally known asthe Arnold steam sterilizer. The usual form is illus-trated in Figs. 6 and 7. Fig. 6 shows the appearance. Fig. sLautenschlager Hot-Air Sterilizer of the ordinary form with the hood off. Fig. 7 showsthe inside arrangement. The two compartments, aand b, are connected by small holes, and a certainamount of water has to be kept here. The water isbrought to a boil and the steam rises through a numberof holes in the bottom (c) into the chamber (d). Thesteam condenses at the top and returns between two BACTERIOLOGICAL TECHNIC 13 sheet-copper walls (e, e) to the large compartment(&). Larger forms on the same principle are in use(Fig. 8). The media to be sterilized are placed in the largechamber {d, Fig. 7). The water is then heated untilsteam is generated, and the action of the steam on themedia is continued for 20 minutes from the time steam
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