APPENDIX 367 



Sodium hydroxide solution for cleaning glassware and 



absorbing C02 : 



Sodium hydroxide, sticks 100 gms. 



Water 1000 c.c. 



Use only once if the glassware is very dirty. 



This solution is invaluable for cleaning greasy flasks, 

 pipettes, etc. 



Caution. This solution should not be left in contact 

 with any glassware longer than thirty minutes as it etches 

 the glass. 



A sodium hydroxide solution of this strength is very 

 corrosive, attacking cloth, laboratory desk tops, etc., and, 

 therefore, should be wiped up immediately if spilled. 



This strength may also be employed to absorb C0 2 

 in fermentation tube cultures of gas-producing organisms. 



STANDARD SOLUTIONS 



A. Preparation of N/10 Na 2 CO3 from titration against 

 which normal acid is prepared. 



1. Dry finely powdered chemically pure Na 2 CO,3 in a 

 drying oven at 105 C. for two hours. 



2. Weigh out carefully and as accurately as possible 

 5.3 gms. of the dried salt. 



3. Dissolve in distilled water which has been boiled 

 previously to expel C0 2 and then cooled. 



4. Make up solution to one liter, using a calibrated 

 volumetric flask and observing temperature for which the 

 flask was calibrated. 



5. Keep this N/10 solution of Na 2 COs in a stoppered 

 bottle. It should be used as soon as possible after prepara- 

 tion, as the Na 2 COs acts upon the glass and thus deterio- 

 rates. 



B. Preparation of N/l, N/10 and N/20 HC1. 



1. Measure out 77.5 c.c. HC1 (sp.gr. 1.20) or 138 c.c. 



