PRINCIPLES OF FRACTIONAL DISTILLATION. 23 



bers, or combine with much soda. This saponification is roughly 

 proportional to the residue not distilling below 185 C. 



The results on the crude oils (Table 3) differ from those on the 

 refined products only in degree. The crude oils have somewhat higher 

 specific gravities, absorb less iodin, and smaller proportions distill be- 

 low 170 C., while the color is deeper than in the refined oils. The 

 figures on crude oils show that as a rule they contain but little more 

 heavy oils than the refined samples. In other words, but little has 

 been accomplished in improving the product except by lightening 

 the color. This is additional evidence that not enough care is 

 exercised in refining. 



PINE OILS. 



"Pine oil" is the term applied to the heavier oils contained in crude 

 wood turpentine. The term is more properly limited to the heavy oils 

 of the steam-distilled crude oil. The heavy oils of crude destructively 

 distilled wood turpentine are chiefly the heavier portions of rosin 

 spirits and rosin oils. 



Until very recently pine oil was almost entirely a waste product and 

 the producer had some trouble in disposing of it. It is now finding 

 more extensive use in paints, varnishes, and medicine, and in the 

 manufacture of drugs and chemicals. Analyses of these oils, crude 

 and refined, and also of refining still residues are given hi Table 2, 

 page 60. The samples which have been examined in this laboratory- 

 have specific gravities of from 0.889 to 0.944, a refractive index vary- 

 ing from 1.4765 to 1.4855; the initial distilling turpentine, when 

 water is not present, ranges from 170 to 210 C. and the major por- 

 tion generally distills between 200 and 215 C. The iodin values 

 are much lower than those of the refined wood turpentine, while the 

 saponification numbers vary about like those of gum spirits. 



PRINCIPLES OF FRACTIONAL DISTILLATION. 1 



When a mixture of liquids is distilled the vapors which arise always 

 contain a larger proportion of the lighter or low boiling constituents 

 and a smaller proportion of the higher boiling constituents than does 

 the remaining liquid, but rarely, if ever, under commercial conditions, 

 do they consist of these lower boiling constituents alone. The com- 

 position of the vapors which arise from the liquid bears a very definite 

 relation to the composition of the liquid in the still. The greater the 

 proportion of the heavy constituents in the liquid, the greater their 

 proportion in the vapor. When an ordinary pot still, therefore, is 

 employed even the first portion which passes over carries with it more 

 or less of the higher boiling constituents. The proportion of these 



i For extensive discussions of the subject of distillation see Hausbrand, "Verdampfen.Kondensleren, 

 und Ktthlen;" Rechenberg, " Gewinnung und Trennung der aetherischen Oele; " and Young, " Fractional 

 Distillation." 



