The figures for direct cooling of the extract are 

 interesting only in showing the necessity of salting 

 out the soap with stronger caustic. The filtrate 

 losses were high and varied inversely as the excess 

 of alkali left in the extract after preliminary steam- 

 ing. In Expt. 6, for instance, where the caustic 

 was nearly all neutralized, the rosin remaining in 

 solution amounted to 20.2 per cent, of the total. 



From 10 to 12 per cent of the rosin was removed 

 in the first washing of the chips. This treatment 

 must therefore be looked upon as an important 

 step in the process. It was found that 80 or 90 

 per cent of this rosin soap could be recovered by 

 precipitation with caustic. An industrial cycle 

 might involve the salting out of the resinate in 

 this way. An alternative would be the addition 

 of enough caustic soda to the first wash liquor to 

 allow its use directly as the alkali liquor for extrac- 

 tion of the wood in the succeeding cycle. This 

 would permit the precipitation ' of the inherent 

 resinate in the next " direct extract." 



From the direct extract and the first wash liquor 

 it was possible to recover about 85 per cent of 

 the total rosin in the wood in the form of rosin 

 soap precipitate, salted out of solution by means 

 of caustic soda. 



Comparatively little rosin was obtained from the 

 second wash liquor and this step would hardly be 

 justified in practice. 



The unsaponified rosin, determined by ether ex- 

 extraction of the washed, dried chips, indicates the 

 efficiency of the alkali extraction. In Expt. 3, 

 7.8 per cent of the rosin was left undissolved by 

 reason of the premature neutralization of the small 

 amount of caustic used. In Expt. 7 the sodium 

 carbonate failed to penetrate the wood in the time 

 allowed for steaming and 8 per cent of the rosin 

 was retained in the free state by the chips. Experi- 

 ments 4, 5 and 6 represent practically perfect 

 extractions of rosin. 



The "balance" includes 3-5 per cent of soluble 

 resinate retained by the chips after the two wash- 

 ings and small quantities of soapy liquor surging 



45 



