40 BULLETIN 1003, U. S. DEPARTMENT OF AGRICULTURE. 



PINE OIL. 



Pine woods contain oils other than those entering into the composi- 

 tion of commercial spirits of turpentine. These oils, collectively 

 spoken of as pine oil, are liberated more or less completely from 

 the wood in their original form, along with the turpentine con- 

 stituents proper. This pine oil is a complex substance made up to 

 a large extent of oxygenated derivatives of the terpenes (turpentine 

 constituents), and has a comparatively high boiling point and spe- 

 cific gravity. The characteristic odor of pine wood is due chiefly 

 to the presence of this oil, in conjunction with turpentine. The 

 characteristic odor of wood turpentine is also due to small quan- 

 tities of pine oil present. The quantity of this oil recovered is 

 always relatively small, varying from a total of 3 gallons from a 

 cord of very rich stumpwood to less than 1 gallon from a cord of 

 dead, down wood and poor stumps. It is necessary to remove or 

 separate this oil as completely as possible from the turpentine, be- 

 cause it does not evaporate readily, and a turpentine containing even 

 a small percentage of it will remain sticky or "tacky" after drying. 

 Its value as a thinner in the paint and varnish industry would be 

 affected accordingly. 



The sum of the total refined turpentine and pine oil recovered 

 from the crude first turpentine amounts, on an average, to 92 per 

 cent, and that from the crude second turpentines to TO per cent. On 

 the basis of the average yields from rich and medium stumpwood, 

 this would amount to 13.5 and 7.8 gallons a cord for the first crude 

 turpentine, and 8.3 and 5.7 gallons for the second crude turpentine. 

 These are the results obtained when the steam distillation is con- 

 tinued to the point where the oil layer makes up 5 per cent of the 

 total distillate coming over at the time. By continuing the distil- 

 lation to exhaustion, or until no more oil is carried over by the 

 steam, an additional 5 or 8 per cent of pine oil may be recovered. 

 Considerations for economy of operation did not warrant the carry- 

 ing of the distillation to this state of completion. The composition 

 of the pine oil progressively changes, so that the portion coming over 

 at the close of the distillation is heavier than that passing over 

 at the earlier stau 



ALKALI RESIDUUM. 



On prolonged standing the black, alkaline liquid remaining from 

 the distillation separates into an aqueous layer and a thick, oleagi- 

 nous, soaplike mass which floats on top of the water. This mass 

 will be designated " alkali residuum." Dissolved in the aqueous layer 

 is a small proportion of what appears to be creosote bodies. The 

 alkali residuum, which is essentially an impure rosin soap, dissolves 

 in wait -i- to form a colloidal solution of great stability that exhibits 



