26 DISTILLATION OF RESINOUS WOOD BY SATURATED STEAM. 

 a **.r FRACTIONATION OF THE OIL DURING DISTILLATION. 



Some very interesting conclusions as to the manner in which the 

 volatile oil leaves the wood can be obtained by comparing the values 

 of the specific gravity of various portions of the distillate. As pre- 

 viously stated, the specific gravity of the oil was determined from 

 each liter of distillate or from as many liters as were necessary to 

 furnish the amount of oil required for a determination. Figures 5, 6, 

 and 7 show these values of the specific gravity obtained in runs 16, 

 20, and 7, respectively, plotted against the percentages of the total 

 oil obtained. 



Figure 5 shows the changes in the specific gravity of the oil obtained 

 during the distillation of a charge of sawdust, first at atmospheric 

 pressure, and then at 40 pounds pressure. The first portions of the 

 oil were nearly pure turpentine, but after about 44 per cent had been 

 distilled the gravity increased rapidly, indicating the presence of pine 

 oil in increasing quantities; when the distillation was from about 67 

 per cent to 83 per cent complete, the oil was nearly pure pine oil. 

 The part of the curve up to 83 per cent resembles very closely a curve 

 obtained from the steam distillation of a crude turpentine; that is, 

 the presence or absence of the wood seems to have no effect on the 

 manner in which the volatile oils are distilled. A difference is seen, 

 however/ in that portion of the curve beyond 83 per cent ; after prac- 

 tically all possible oil has been removed by a continuous distillation at 

 atmospheric pressure, interruption of the distillation, followed by a 

 further distillation under the same pressure, produced a small fur- 

 ther yield of oil with a lower gravity, and, on increasing the steam 

 pressure, still more oil was obtained with a still lower gravity. This 

 indicates that both the interruption of the distillation and the 

 increase in steam pressure brought more oil into contact with the 

 steam and that this oil contained some of the low-gravity turpentine 

 material. 



A very different behavior is shown in figure 6, which represents the 

 distillation of chips 1 inch X I inchx i inch at a pressure of 70 pounds. 

 In distillation under these conditions there was much less tendency 

 for the oil to be separated as distilled, the gravity of the very first 

 fraction being higher than that of pure turpentine and the gravity 

 of the later fractions never reaching that of pure pine oil; that is, 

 the turpentine and pine oil distilled together throughout the run. 

 This indicates that new supplies of volatile oils were brought into con- 

 tact with the steam more or less continuously throughout the dis- 

 tillation; had it been otherwise the turpentine would have distilled 

 first and the last fractions would have been nearly pure pine oil. 



A still more striking picture of the variation in the gravity of the 

 distillate due to changes in the conditions of distillation is shown in 



