26 



WOOD TUKPENTINES. 



and seems to take place mostly during the very last part of the distil- 

 lation when the amount of oil in the distilling flask has become very 

 small and when there is, therefore, a better chance for the sides of the 

 ilask to become superheated. 



CHANGES IN COMPOSITION AND INTERPRETATIONS OF CURVES. 

 TURPENTINES CONTAINING NO HEAVY OILS. 



When a turpentine containing no heavy oils is distilled by direct 



heat the undistilled residue left in the 

 flask will contain a small amount of 

 heavy oils, owing to changes occurring 

 during the distillation, and the specific 

 gravity and index of refraction of this 

 residue will be higher than those of the 

 last distilled fraction; the curves will, 

 therefore, seemingly indicate that small 



eo| [)-|-| [- amounts of heavy oils were present in 



| _J jj the original turpentine, but from the 



| 5 o| 11 I I curves of figures 11 to 13 the effect 



of the changes, which occurred during 



EH || I I 1 fl I \ 1 I I the distillation, can be determined, and 



the interpretation of the curves can be 

 altered to correspond. For instance, 

 in the distillation of 95 per cent of a 

 turpentine containing no heavy oils, the 

 production of heavy oils during the 

 distillation will be sufficient to increase 

 the gravity and index of the residue of 

 5 per cent by 0.0035 and 0.0040, respec- 

 tively. Of course, if the residue is 

 made smaller say 2 per cent then the 

 apparent effect would be greater, since 

 there is a chance for more polymeriza- 

 tion during the distillation of that portion between 95 and 97 per 

 cent ; and the proportion of heavy oil to turpentine oil in the undis- 

 tilled residue is increased and hence the physical properties in- 

 creased as the distillation progresses. It is therefore necessary to 

 leave about 5 per oent of oil undistilled in order to be able to correct 

 accurately for the effect of polymerization. 



TURPENTINES CONTAINING HEAVY OILS. 



When, hoAvever, the turpentine to be distilled contains some heavy 

 residue (as for instance in fig. 2) the conditions are different; the 

 terpenes may all be distilled over, and the residue left in the flask 



I5P1CIF 

 )E 



160 165 170 175 180 185" 190" 195 

 O .86 .87 .88 .89 .90 .91 3Z .93 

 O Ufc8 U70 W72 W74 W76 M-18 I.A8O 



FIG. 13. Alteration in physical 

 properties of a scum turpentine 

 due to direct distillation. 



