54 WOOD TURPENTINE. 



The bureau has found in laboratory experiments that when the, 

 wood is prepared to pass a J-inch screen the oils are removed com- 

 pletely in less than two hours steaming and no more is obtained or 

 cooking. When prepared to pass an inch screen, but not a J-incr. 

 screen, the oils are removed in from two to two and one-fourtt 

 hours steaming, and no more is obtained on further cooking. If the 

 chips will pass a 2-inch screen, but not an inch screen, it requires 

 three hours steaming and 12 per cent of the total oils is obtained ir 

 subsequent cooking. With properly prepared wood, the time foi 

 removal of turpentine is reduced at least one-third. The advantage* 

 of reducing the wood to a proper size and using a rotary have beer 

 demonstrated in the laboratory; 0.25 to 0.88 per cent of oils were 

 recovered from the chips which had been steamed in a fixed retort 

 The smallest recovery was from chips passing a J-inch screen anc 

 the largest amounts from chips not passing a 1-inch screen. The 

 chips should, therefore, be screened before they are placed in the 

 digester and those which are too large should be made smaller b} 

 regrinding, or, preferably, by shredding. 



Under proper conditions the turpentine can be steamed out of the 

 chips in about three hours. So far as the removal of the turpentine 

 is concerned, only a small pressure need be carried on the rotary 

 until the crude oils are off; 40 pounds pressure applied intermittently 

 is ample. The pressure may then be raised for the purpose of cooking 

 the wood. The wood should not be reduced to chips and stored as 

 such for any length of time before steaming, as cut-up wood loses 

 turpentine quite rapidly, especially in warm weather. (Hoggec 

 wood has been known to lose half the turpentine in one week.) IJ 

 the grinding plant can not deliver the chips to the digester witt 

 sufficient rapidity, chipping may be begun before the digester is readj 

 to receive the charge, and the chips held for a short time in an over- 

 head bin, from which they can be spouted to the digester. Large 

 amounts of chips should not be so stored, however, and losses due tc 

 volatilization or fire must be guarded against. 



Two digesters, each holding 8 cords (12 to 16 tons) of chips, can 

 handle at least 50 cords (75 to 100 tons) of wood per 24 hours, three 

 cooks being made in each digester. If lightwood is used, from 400 tc 

 1,000 gallons of crude oils should be obtained by steaming the chips. 

 From the black liquor by destructive distillation, from 1,500 tc 

 5,000 gallons of oils, consisting of rosin spirits and rosin oils mixed 

 with oils (chiefly phenols and cresols) derived from the ligneous 

 material removed by the soda, are obtained. The full amount oi 

 methyl alcohol usually obtained by destructive distillation of pine 

 wood, together with traces of acetic acid, are also contained in the 

 aqueous distillate from the black liquor. From the residue of the 

 distillation of the black liquor, sodium carbonate is dissolved and 

 recausticised in the usual way. 



