8 LABORATORY GUIDE IN BACTERIOLOGY 



SECTION 3 



PREPARATION AND CLEANING OF GLASSWARE 



Culture tubes, flasks, fermentation tubes, and petr 

 dishes must be free from organic matter, acids, and 

 alkalis. They should be cleaned as follows : 



1. Immerse them in a vessel containing soapsuds or 

 soap powder, boil 10 to 15 minutes, then clean them 

 with a tube brush. Or immerse them for an hour in a 

 solution of potassium bichroniate and sulphuric acid: 



Potassium bichromate 60 parts 



Water 300 parts 



Concentrated sulphuric acid 460 parts 



The sulphuric acid should be added slowly with con- 

 stant stirring. 



2. Rinse in tap water. 



