CLEANING GLASSWARE 3 



paper. Sometimes there appears to be a film on the surface 

 of the cover glasses which interferes in making hanging-drop 

 preparations. Sometimes this can be overcome, after they are 

 wiped out of the alcohol, by placing them in a Petri dish with- 

 out the cover and heating them in the dry-air sterilizer at a 

 temperature of 1 60° to 1 80° C. for one hour. After they have 

 cooled, replace the cover and allow the cover glasses to remain 

 in the Petri dish (a glass jar or other closed dish may be used) 

 until used. (When a drop of water or bouillon is spread upon 

 a properly cleansed cover glass it does not roll up in droplets, 

 but v\-ill remain in a thin, even layer on the surface.) 



Slides can be cleaned very satisfactorily by washing them 

 in hot soapsuds, rinsing them in hot water, and wiping them 

 \^'ith a soft cloth. 



(f) Cleaning used culture apparatus. Place the tubes, flasks, 

 or Petri dishes containing old cultures in a water bath, cover 

 them with water, add a little sal soda (about an ounce to a 

 gallon of water), and boil for 20 minutes. Pour off the water 

 and empty the tubes, after which again boil them for 5 minutes 

 in clean soap and water. Then wash and treat with the clean- 

 ing mixture the same as the new tubes. Cultures of spore- 

 bearing pathogenic bacteria, such as those of anthrax, should 

 be destroyed by heating in the autoclave at a temperature of 

 at least no" C. for half an hour before the tubes are emptied 

 and washed. 



4. A method for cleaning cover glasses for flagella stain. 

 For this work the ordinary method of cleaning cover glasses is 

 not sufficient, although the heating will often give a perfectly 

 satisfactory' cover glass. The following treatment was first 

 highly recommended t(Tme by Dr. Erivin F. Smith, and later 

 modified by Johnston and Mack. First clean the cover glasses 

 by the ordinary method, after which boil them in an agate cup 

 or glass beaker in a 5 % solution of caustic soda for 10 minutes. 

 After cooling, rinse thoroughly in distilled water, place in a 

 beaker, and cover with a 10% solution of hydrochloric acid 



