APPARATUS, MATERIAL, AND REAGENTS. 



The apparatus stands upon three legs, and is heated from below with 

 two or three Bunsen burners, or a Fletcher's 

 burner. It is employed for sterilising 

 nutrient media in tubes or flasks, for cooking 

 potatoes, or hastening the filtration of agar- 

 agar. When the thermometer indicates 

 100 C. the lid is removed, and test-tubes 

 are lowered in a wire basket by means of 

 a hook and string, and the lid quickly re- 

 placed. Potatoes or small flasks are lowered 

 into the cylinder in a tin receiver with a 

 perforated bottom, which rests upon the- 

 grating and admits of its contents being 

 exposed to the steam. A larger model is 

 shown in Fig. 33. 



Hot-air Steriliser. A cubical chest of 

 sheet iron with double walls, supported on 

 four legs ; it may also be suspended on the 

 wall of the laboratory, with a sheet of 



FiG.250.-KocH's STEAM- Asbestos intervening (Figs. 251 and 252). 



It is heated with a rose gas-burner from 

 below, and the temperature of the interior in- 



STERILISEE. 



clicated by a thermometer inserted through 

 a hole in the roof ; in a second opening a 

 gas regulator can be fixed. Test-tubes, 

 flasks, funnels, cotton wool, etc., may be 

 sterilised by exposure to a temperature 

 of 150 C. for an hour or more. 



FIG. 251. HOT-AIR STERILISER. 



FIG. 252. SECTION OF HOT- 

 AIR STERILISER. 



