FORMULAE AND METHODS 



CLEANING GLASSWARE 



1. ALL glassware must be thoroughly cleaned before it 

 is ready to use. Test-tubes, Petri dishes, flasks, and similar 

 glassware should be boiled in a 5 per cent, soda solution 

 or washed in hot soapsuds until free from organic matter. 

 When it is desirable to use very clean glassware, immerse 

 for ten minutes or longer if possible in the dichromate 

 solution. 



Potassium (K 2 Cr 2 O 7 ) or sodium dichromate (Na 2 Cr 2 O 7 ) ... 80 gm. 



Water 300 c.c. 



Sulphuric acid (H 2 SO 4 ) 460 c.c. 



Note. Dissolve the dichromate in warm water and, when cool, add 

 slowly concentrated sulphuric acid. If properly prepared, the liquid should 

 be thick, with small crystals. It may be used repeatedly, provided the 

 crystals 'are present. 



2. After removing from the cleaning solution rinse 

 thoroughly in distilled water. 



3. Dirty cover-glasses and slides may be treated in the 

 same manner. Drop these, one at a time, into the dichro- 

 mate mixture and allow to remain for several hours. Re- 

 move from this solution, wash, and wipe with a soft, clean 

 cloth. 



4. A simple and more rapid method, suitable for general 

 work, is to rub the slides with moist Bon Ami, and when 

 dry to polish them with a clean cloth. 



5. In order to remove fat pass the cover-slips through a 

 flame. Where it is desirable to have very clean slides and 



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