. A laboratory guide in bacteriology, for the use of students, teachers, and practitioners. trong cylinder made of BACTERIOLOGICAL TECHNIC IS iron. Some forms have a cover, others a door on oneside. A basket, or a set of shelves, is on the gauge indicates the pressure and temperature. Asafety valve opens automatically when the desiredpressure is reached. Two _ yOi> forms are illustrated inFigs. 9 and lo. Before using the auto-clave the inside should beexamined. It must beclean and contain a suflS-cient quantity of cleanwater. Water containingimpurities is liable to foamup when boil
. A laboratory guide in bacteriology, for the use of students, teachers, and practitioners. trong cylinder made of BACTERIOLOGICAL TECHNIC IS iron. Some forms have a cover, others a door on oneside. A basket, or a set of shelves, is on the gauge indicates the pressure and temperature. Asafety valve opens automatically when the desiredpressure is reached. Two _ yOi> forms are illustrated inFigs. 9 and lo. Before using the auto-clave the inside should beexamined. It must beclean and contain a suflS-cient quantity of cleanwater. Water containingimpurities is liable to foamup when boiling, wet theplugs, and ruin the the lid is on top, itshould be fastened care-fully by tightening thethumbscrews. In orderto distribute the pressureof the lid uniformly thediametrically oppositescrews shoidd be tight-ened simultaneously. Thevalve should be open andleft open until the steamhas escaped for about oneminute. Then the valveis closed and when the desired pressure has beenreached, the gas should be turned down so as tomaintain pressure for the requisite length of Fig. 9 Autoclave a. Steam valve d, d. Thumbscrews h. Safety valve e. Bunsen burnee c. Gauge and opening l6 LABORATORY GUIDE IN BACTERIOLOGY At the end of this period the gas is shut off and thepressure allowed to decrease gradually. The valveshould not be opened, nor the lid removed, untilatmospheric pressure has been restored, otherwise thesudden release of pressure would cause the media to boil suddenly and pushthe plugs out of place. When large autoclavesare used (Fig. lo) pro-vision must be made forproper circulation of air,or air cushions formand media will not besterilized. If an apertureremains in the outlet thedischarge of air is facili-tated. Attachment of avacuum pump is oftendesirable to remove all serum or eggmedia are the most difiS-cult to sterilize. The tem-perature of coagulation ofthese media is relativelylow, and sudden heatingcauses the mass to breakup, form bubbles
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