Mar., 1921
T N E J O U R X A L OF I N D U S 2 ' R I . A L A N D E N G I N E E R I N G C H E M I S T R Y
pigment from t h e fiber, which, i f ground wood pulp be absent, and if t h e concentration of t h e caustic Rc regulated, and if t h e temperature be not too high, serves t o remove R large proportion of carbon ink. Too great ii concentration may bring about some mercerization. More weakly alkaline solutions, f o r example, sodium silicatc, sodium phosphate, boras, soap, etc., also lift t h e ink in part a n d d o little damage t o tile fiber. Hovixwer, t h e detergent effect calls for scouring or rubbing, which so embeds t h e carbon in t h e fiber as t o make it almost impossible t o sep:irate t h e two. Certain solvcnts. as kerosene or gasoline. tend t o loosen t h e iiik by dissolving t h e binder. This may be combined with irn alkaline solution, for example, a borax or a soap solution. During agitation t h e suds or skim, which forms on t h e surface of t h e water and entangles t h e carbon particles, may IJCwnshed :%Nay. Rosin is extensively used as a filler and binder foit h e fibers of t h e paper, which have n "surface." As mentioned, some oi t h e cheaper magazine papers contain wood pulp, which retains natural gums and resins. They servo in part as hinders for t h e ink pigments. Pinc oil is one of t h e normal solvents for rosin, gums, a n d resins. so its addition t o t h e old printed matter helps materiirlly t
