AUTOCLAVE 



47 



culture media, and thick glass vessels and other apparatus 

 which would crack or be damaged by the high temperature 

 of the hot-air steriliser, are sterilised by steam. The 

 lower chamber of the steamer, below the false bottom, 

 is partly filled with water, which is boiled by means of 

 a Bunsen or ring burner. Above the false bottom the 

 culture media or apparatus are 

 placed, and are sterilised by the 

 steam at 100 C. which fills this 

 space. 



Here again an inexpensive sub- 

 stitute may be devised ; the 

 ordinary kitchen saucepan with 

 steamer will do well for many 

 purposes, while a " warren pot " 

 answers admirably. 



Autoclave (Fig. 4). This is 

 most useful for many purposes, 

 but it is expensive and not a 

 necessity, as the steam steriliser 

 will serve almost every purpose 

 for which the autoclave is em- 

 ployed with the expenditure of 

 a little more time and trouble. 

 It consists of a strong boiler of 

 brass or gun-metal with a removable lid, which is attached 

 to the boiler by means of screw-bolts. The lid is provided 

 with a safety valve, a gauge for indicating the pressure 

 and temperature, and a stopcock to relieve the pressure 

 if required. A small quantity of water is placed in the 

 bottom, and the media or apparatus to be sterilised having 

 been introduced, the lid is screwed down. It is heated 

 by means of one or more Bunsen burners, which are 

 turned down when the required temperature has been 

 reached. The temperature usually employed is about 



FIG. 4. Autoclave. 



