QUALITATIVE AND QUANTITATIVE ANALYSIS 55 



If, for instance, the weight of ammonium sulphate is 0.6675, the 

 factor of the solution is 1.01 13 + . This means that 10 cubic 

 centimeters of the solution is equivalent to 10.113 cubic centi- 

 meters of normal solution. 



Normal Sodium Hydroxide Solution 



To prepare a normal solution of sodium hydroxide, weigh out 

 roughly 45 grams of caustic soda (wash off the carbonate from 

 the surface of the sticks of alkali) and dissolve in a little more 

 than a liter of water. Allow this solution to stand until cool 

 and titrate against A^/5 acid potassium phthalate. The prepa- 

 ration of N/5 phthalate follows : 



Molecular weight of KHC8H4O4 = 204.14. 



Normal phthalate = 204.14 grams in 1,000.0 cubic centimeters 

 of water. 



Fifth normal phthalate = 40.83 grams in 1,000.0 cubic 

 centimeters of water. 



Weigh out 20.414 grams of dried (at 110 to 115°C.) phthalate. 

 Transfer to a 500-cubic centimeter flask. Dissolve in water 

 and make up to volume. 



To standardize a normal solution of NaOH, measure 50 cubic 

 centimeters of the N/5 phthalate solution with a pipette and 

 titrate with phenolphthalein as the indicator; 50 cubic centi- 

 meters A^/5 phthalate = 10 cubic centimeters of N/1 NaOH. 



Example. — 50 cubic centimeters N/5 phthalate = 9.36 cubic centimeters 

 of the approximately N/1 NaOH. ^ 



^ = 1.068 factor for iV/1 NaOH. 



Make necessary dilution if an exact N/1 solution is desired. 



To standardize an N/10 NaOH solution, dilute 20 cubic centimeters of 

 phthalate solution to 100 cubic centimeters and titrate 25 cubic centimeter 

 aliquots with the alkali. Calculate the factor as above or dilute if an exact 

 N/10 solution is desired. 



Standard (iV/6) Solution of Oxalic Acid 



To prepare a standard, iV/6 solution of oxalic acid, dissolve 

 63 grams of C.P. oxalic acid [(COOH)2-2H20] in 1 liter of dis- 

 tilled water by warming. Then dilute to exactly 6 liters with 

 distilled water. This solution is standardized against the sodium 



