CLEANING GLASSWARE 3 



Ion is spread upon a properly cleansed cover-glass it will not 

 roll up in droplets, but remain in a thin, even layer on the 

 surface.) 



Treat the slides with the cleaning mixture in the same man- 

 ner as the cover-glasses. They may, however, be wiped directly 

 out of the rinsing water. Slides can often be cleaned very satis- 

 factorily by washing them in hot soap-suds, rinsing them in 

 water, and wiping them with a soft cloth. 



(/) 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 

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

 water and empty Che tubes, after which again boil them for 

 5 minutes in clean soap and water. Then wash and treat with 

 the cleaning 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 tempera- 

 ture of at least 110° 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, althougli the heating will often give a perfectly 

 satisfactory cover-glass. The following treatment was highly 

 recommended to me by Dr. Erwin F. Smith. First clean the 

 cover-glasses by the ordinary method, after which boil them in 

 an agate cup or glass beaker in a 10% solution of caustic 

 soda for 5 minutes. After cooling, rinse the cover-glasses 

 thoroughly in distilled water, place them in a beaker and 

 cover them with a i % solution of hydrochloric acid, heat to 

 the boiling point, and allow to stand for several hours (over 

 night or longer) . Then pour the acid off and rinse the cover- 

 glasses several times in distilled water, and finally in alcohol. 

 Wipe them out of the alcohol as they are needed. 



6, Laboratory Notes. — In this and all subsequent exercises 

 careful notes should be taken on the work done. When, how- 



