PRODUCTION OF SULPHITE PULP FROM SPRUCE. 23 
liter. Two hundred cc of this solution make 4 liters of approximately 
{g iodine. This is then standardized against, sodium thiosulphate 
solution. 
N 
PREPARATION OF 76 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 SO,. 
A 300 ce Erlenmeyer flask is filled with about 150 cc distilled 
NG 
water and enough 7¢ 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 SO, present and every cc on the burette reads to one-tenth of 
1 per cent. 
DETERMINATION OF FREE SO,. 
A 300 cc Erlenmeyer flask is filled with about 150 ec of distilled 
water and enough i6 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 SO,. The difference between the free and total gives the SO, 
present combined with lime, and multiplying the amount of combined 
SO, by 0.875 gives the amount of lime (CaO) in combination. 
