18 BULLETIN 620, U. S. DEPARTMENT OF AGRICULTURE. 
EFFECT OF VARYING TOTAL SULPHUR DIOXIDE. 
Cooks were made varying the amount of total SO, from 3.02 to 6.98 
per cent, but in each case the ratio of free to combined SO, was kept 
at 4 to 1 and the temperature at 135°C. Figure 9 gives the curves 
o 
(77) 
a =s=<5 aap =s=se=4-- Bee geu gece 
5 Hon hse | | Perec ci el 
4 | 
FECES 
(BG kab Vimes Hee SiGe 0S0C SSS Sa Se 
LSS PORN Paes SS DESO SSE 
ELM Seenneee Rte [cee aa AGE AR Ceo 
PE ells BL SIs pee) fPShencowee 
DCSE BEGEE BS 4) 
200. 9 30 44 46 
PARTS BLACK DURATION OF cook — Hours YIELD OF UNSCREENED 
PULP — PERCENT 
B 
PEE HEE 
HG —- aa Mie) eee eta 
Bee | (et 96 8 a ps PSs flea 
a NGI a 
Tota. SO, 
42 so 6060 i 2 3 4 
YIELD oF SCREENED PULP — ‘PERCENT SCREENINGS—PERCENT BLEACH — PERCENT e 
Fic. 9.—Effect of varying the amount of total SO2 in the cooking liquor. 
showing the effect on the different factors studied, parts black, dura- 
tion of cook, yields, and bleach consumed. While these cooks were 
made with the ratio of free to combined SO, of 4 to 1, the actual 
amount of combined sulphur dioxide in the apa liquor decreased 
with the total, as shown in Table 3. 
