PRODUCTION" OF SULPHITE PULP PROM SPRUCE. 23 



liter. Two hundred cc of this solution make 4 liters of approximately 



N „-.-.,■.. N 



j^ iodine. This is then standardized agamsty^ sodium thiosulphate 



solution. 



N 

 PREPARATION OF j^ SODIUM THIOSULPHATE. 



Weigh out 24.7 grams of sodium thiosulphate, dissolve in water, 

 and dilute to 1,000 cc. This is standardized according to any of the 

 standard methods. 



DETERMINATION OF TOTAL S0 2 . 



A 300 cc Erlenmcyer flask is filled with about 150 cc distilled 



N . 

 water and enough th iodine solution added so that only about 2 



cc of the iodine solution will complete the titration. Two cc of 

 the liquor to be analyzed are then added to this and the titration 

 completed, using starch solution as an indicator. This gives the 

 total S0 2 present and every cc on the burette reads to one-tenth of 

 1 per cent. 



DETERMINATION OF FREE S0 2 . 



A 300 cc Erlenmeyer flask is filled with about 150 cc of distilled 



N 

 water and enough vs sodium hydrate added so that only about 2 cc 



will complete the titration.. Two cc of the liquor to be analyzed are 

 then added and the titration completed using phenolpthalein as an 

 indicator. Each cubic centimeter is equal to one-tenth of 1 per cent 

 of free S0 2 . The difference between the free and total gives the S0 2 

 present combined with lime, and multiplying the amount of combined 

 S0 2 by 0.875 gives the amount of lime (CaO) in combination. 



