EXPERIMENTAL METHODS. V 



the distillation, never quite reaching 100 C., however, as long as any 

 of the turpentine or pine, oil remains undistilled . 



(3) If the pressure is increased the temperature will be increased; 

 the temperature depends upon the pressure 'and on the concentrations 

 of the turpentine, pine oil, and rosin; it will, however, never reach 

 the steam temperature corresponding to the pressures used as long 

 as any turpentine or pine oil remains undistilled. 



(4) The proportion of oil to 'water in the distillate will decrease as 

 the distillation progresses; this proportion is influenced only by the 

 composition of the oleoresin at various stages of the distillation. 1 



In these deductions it is considered that the system is in complete 

 equilibrium; under such conditions the behavior of oleoresin when 

 distilled with steam can be foretold with considerable accuracy, but 

 in the distillation of wood containing oleoresin there is a disturbing 

 factor which necessitates investigation of several variables (p. 18). 

 This disturbing factor is the difficulty of keeping a complete equi- 

 librium between the oleoresin and the steam, since the wood surrounds 

 the oleoresin and tends to keep the steam from coming in contact 

 with it. 



The effects of the size of chips and of the rapidity of distillation 

 and (aside from temperature changes) the effects of steam pressure 

 are due to the influence of these factors on the completeness of 

 equilibrium between the oleoresin and the steam, rather than to their 

 influence on the behavior of the oleoresin and steam when completely 

 in equilibrium. 



EXPERIMENTAL METHODS. 

 GENERAL PROCEDURE. 



The general procedure was to distill charges of the same sized chips 

 under different conditions, and of different sized chips under identical 

 conditions, and to note carefully the variations in the results of the 

 distillations. It was not practicable to make all the runs on exactly 

 comparable material, because a large number of charges of equal 

 resin content could not be secured, and because the material could not 

 be kept without some loss of volatile oil by evaporation. The runs 

 were therefore made in groups with comparable material in each 

 group; the results from each group were made comparable to some 

 extent with those from other groups by a comparison of the resin 

 content of the different groups. This was readily accomplished by 

 distilling the sawdust obtained in the preparation of the material for 

 each group, as this sawdust was a good average sample of the whole 

 group. 



1 A change in the pressure at which the distillation is carried on might change the proportion of water to 

 oil in the distillate, but this change would be slight and there is not sufficient information available to 

 decide even the direction of this change. 



50681 Bull. 10912 2 



