MOIST HEAT 37 



as cannot be dealt with by dry heat or the actual 

 furnace. Sterilisation by means of superheated steam 

 is carried out in a special boiler Chamberland's 

 autoclave (Fig. 30). The autoclave consists of a stout 

 copper ylinder, provided with a copper or gun-metal 

 lid, which is secured in place by means of bolts and 

 thumbscrews, the joint between the cylinder and its 

 lid being hermetically sealed by the interposition of a 

 rubber washer. The cover is perforated for a branched 

 tube carrying a vent cock, a manometer, and a safety 

 valve. The copper boiler is mounted in the upper half 

 of a cylindrical sheet-iron case two concentric cir- 

 cular rows of Bunsen burners, each circle having an 

 independent gas-supply, occupying the lower half. 

 In the interior of the boiler is a large movable wire 

 basket, mounted on legs, for the reception of the 

 articles to be sterilised. 



To USE THE AUTOCLAVE. 



1. Pack the articles to be sterilised in the wire 

 basket. 



2. Run water into the boiler to the level of the bot- 

 tom of the basket; also fill the contained flasks and 

 tubes with water. 



3. See that the rubber washer is in position, then 

 replace the cover and fasten it tightly on to the auto- 

 clave by means of the thumbscrews. 



4. Open the vent cock and light both rings of burners. 



5. When steam is issuing in a steady, continuous 

 stream from the vent tube, shut off the vent cock and 

 extinguish the outer ring of gas burners. 



6. Wait until the index of the manometer records a 

 temperature of i2o p C., then regulate the gas and the 

 spring safety valve in such a manner that this tem- 

 perature is just maintained, and leave it thus for 

 twenty minutes. In the more expensive patterns of 

 autoclave this regulation of the safety valve is carried 



