STERILIZATION OF GLASSWARE 25 



Bichromate of potassium 6 parts 



Water 100 parts 



Sulphuric acid 6 parts 



Dissolve the bichromate by heating in an agate kettle. Add 

 the sulphuric acid slowly on account of the heat generated ; after 

 cooling keep in a glass jar. The mixture may be used more than 

 once. 



After thoroughly rinsing and drying, test tubes and flasks are 

 plugged with ordinary non-absorbent cotton. The plugs should 

 not be twisted or creases will form, making possible the entrance of 

 bacteria from the surrounding air. The most satisfactory method 

 is to roll the cotton, which should fit just tight enough to allow 

 one to lift the tube by means of the plug. 



FIG. 5. Hot Air Sterilizer. 



STERILIZATION BY DRY HEAT 



1. Hot Air Chamber. This method is used for all forms of 

 glassware. The hot air chamber (Fig. 5) consists of an outer 

 and an inner covering of sheet iron. At the bottom, in the space 

 between the two jackets, several gas jets are arranged. The 



