    Sentence Lt Generally,’ if pH of scrubbing  liquor. falls: below’ a’ range. of $0 to-'6.0;  additional. reagent i3- required. fo’ maintain  the reactivity of the absorbent.    Sentetioe’ 2i-if pH of. scrubbing liquor  becomés, above a: range ‘of .5.0°-to: 6.0,  additional reagentis reguired.