CLEANING SLIDES AND COVER-GLASSES 3 1 



CLEANING SLIDES AND COVER-GLASSES 



Slides and cover-glasses must be absolutely clean when used in 

 the bacteriological laboratory ; it is especially necessary that they 

 should be free from the slightest trace of grease, for this will 

 prevent fluid from spreading out into a thin and uniform film. 



Slides are best cleansed by dropping them one at a time into 

 strong nitric or sulphuric acid, and allowing them to soak for an 

 hour or more. They are then washed in running water for 

 another hour, soaked in strong ammonia for an hour, and kept in 

 alcohol. As methylated spirit is not so good for this purpose, the 

 use of alcohol is rather expensive ; but it is not absolutely 

 necessary, and the slides may be stored in a solution of ammonia 

 (about I in 10) until required. When about to be used, they are 

 to be wiped dry with an old linen handkerchief kept specially for 

 the purpose. This handkerchief should be as old as possible, and 

 should have been washed until it has begun to fall to pieces. 



Another and more rapid method is to place the slides in a thin 

 glass or earthenware vessel and moisten them with methylated 

 spirit, and then to cover them completely with strong commercial 

 nitric acid, placing the vessel in the open air. In a little while 

 the acid will become very hot and emit copious fumes. When 

 the ebullition has ceased, any fat which may be present will have 

 melted, and will form a pellicle on the surface, whilst other organic 

 materials will have been destroyed. The acid is then to be poured 

 off, taking care to remove the pellicle of grease with it, and a 

 stream of water allowed to fall into the vessel until the acid has 

 been washed away. The slides (and the method is a good one for 

 cover-glasses also) may then be placed in absolute alcohol or 

 methylated spirit, and only require drying to be ready for use. 



Another method which I have recently used and found excellent 

 is to boil them in a 5 per cent, solution of lysol ; they may be 

 allowed to remain in this fluid until required, and are then 

 polished with a handkerchief — and it may be pointed out that 

 thorough friction is a sine qua mn whatever method of cleaning be 

 adopted. Slides and cover-glasses after use may be soaked in the 

 lysol solution, a pot of which should be kept at hand for the 

 purpose ; they will be sterilized and partially cleaned in a few 

 hours. 



When no properly-cleaned slides are at hand, the following 

 method may be adopted, though it is not so good ; Dip the end 



