368 APPENDIX 



HC1 (sp.gr. 1.12) and make up to one liter with distilled 

 water. This makes a solution just a little stronger than 

 normal. 



2. To determine its exact strength, titrate 5 c.c. with 

 N/10 Na2COs, using phenolphthalein as the indicator. 



3. Rim check determinations, which should check within 

 one- or two-tenths of a cubic centimeter. 



4. From results, calculate by proportion how much a 

 liter of the solution should be diluted to make it N/l. e.g. : 



5 c.c. HC1 was neutralized by 55 c.c. N/10 Na 2 C0 3 



.'. HC1 is N/l.l 

 By proportion: 



N/l : N/l.l:: 1000 :x 



a: = 1100 



Hence each liter of the HC1 solution should be diluted to 

 1100 c.c. with distilled water to make a N/l solution of 

 HC1. 



5. N/10 and N/20 solutions of HC1 can be made by 

 making the proper dilutions. Always use calibrated flasks 

 and burettes when making these dilutions. 



C. Preparation of N/l and N/20 NaOH. 



1. Weigh out roughly 41 gms. of chemically pure NaOH. 



2. Dissolve in distilled water, which has been boiled 

 to expel CO2 and then cooled. 



3. Make up to one liter, using a calibrated volumetric 

 flask and observing the temperature for which it was cali- 

 brated. This makes a solution a little stronger than normal. 



4. Determine its exact strength by titration with N/10 

 HC1. 



5. Proceed from this point as in the preparation of 

 N/l HC1. 



6. N/10 and N/20 solutions can be made from the N/l 

 solution as in the preparation of N/10 and N/20 HC1. 



