60 BULLETIN 1003, U. S. DEPARTMENT OF AGRICULTURE. 
the oil during the alkali treatment yields a turpentine having a 
sweeter odor than that obtained without aeration. The other prop- 
erties and the yield of turpentine recovered, however, are not mate- 
~vilally influenced thereby. In refining a crude oil which is heavily 
charged with the decomposition products of destructive distillation, 
aeration to improve the odor may be found advantageous. 
This procedure was followed in refining the various crude turpen- 
tine samples obtained: 
Transfer a 500 cc. portion to a round-bottomed ifiter flask, add 75 ce. of 20 
per cent NaOH solution, and some finely broken pumice. Attach a large reflux 
condenser and heat the contents to and maintain at the boiling temperature, 
over a gas fiame, for one-half hour. When sufficiently cooled, to avoid loss, 
remove the reflex condensér, attach a Hempel column of fairly good size 
filied three-fourths full with short pieces of glass tubing, and a condenser in 
the ordinary position, and distil the contents of the flask with steam in the 
usual manner. The oil coming over to where the ratio of oil to water is 
4 to 6 is first-quality commercial turpentine, ready to enter the trade as such. 
That coming over between the 4 to 6 and 3 to 7 ratio contains a small pro- 
portion of lighter pine-oil constituents, and needs to be distilled a second time 
for their complete removal. The distillation is continued for the recovery of 
4 
‘pine oii to the point where the pine oil forms 5 per cent of the distillate 
coming cver at the time, below which ratio it was not deemed economical to go. 
To determine quickly the proportion of oil to water in the dis- 
tillate it was found convenient to use a coordinate paper diagram ~ 
(fig. 5), in which abscissee are the water readings and ordinates the 
total distillate readings collected during a short interval. Right 
lines are drawn from the origin of coordinates to intersect, at 100 
on the ordinate axis, the points 60, 70, and 95 on the axis of abscisse, 
respectively, these corresponding to the percentage of water in the 
distillate at the transition points. To use the diagram for deter- 
mining the end of, say, the turpentine fraction, the volumes of water 
and total distillate are read. The volumes of water are transferred to 
the horizontal and those of the distillate to the vertical axis. If 
the intersection falls above the 60 per cent water line, the propor- 
tion of oil exceeds 40 per cent, and similar readings are taken at 
suitable intervals until it falls on the line. Similarly, the 70 and 
95 per cent lines determine the end of the other fractions. 
. The odor and color of the refined turpentine samples thus obtained 
were noted, the specific gravity and-refractive index determined, and 
a distillation made from which to judge their quality (Table 18). 
The distillation temperature limits of turpentine are so suscep- 
tible to pressure variation that it is essential, in making such com- 
parisons, to conduct the distillation under normal pressure. The 
laboratory at Moscow, Idaho, being at an elevation of about 2,800 
feet above sea level, it was necessary to increase the pressure in the 
distillmg apparatus accordingly. This is accomplished by means 
