ANALYSIS, BEFINING, AND COMPOSITION. 53 



tained from four of the five samples of crude contained dipentene; 

 it is probable that most wood turpentines will contain appreciable 

 amounts of this substance. In some 75 samples of gum turpentine 

 which have been examined in the Forest Products Laboratory no 

 dipentene has been detected by the method of analysis used. It 

 appears that the presence of dipentene in wood turpentine is not 

 entirely due to the temperature to which the turpentine is subjected, 

 because most gum turpentines have been subjected to temperatures 

 of at least 150 C. during their distillation, and yet crude turpentine 

 No. 2, which was produced at 50 pounds steam pressure (148 C.), 

 contained considerable quantities of dipentene. Dipentene was also 

 found in the volatile oil distilled from lightwood by steam at atmos- 

 pheric pressure. 1 The influence of temperature is indicated by the 

 increased amounts of dipentene in wood turpentines produced at 

 high temperatures. The dipentene in wood turpentine may, then, 

 come from two sources, (1) from the dipentene present in the volatile 

 oil as contained in the wood, and (2) from the transformation of 

 some of the pinene into dipentene by the high temperatures used in 

 the distillation. 2 



LIGHT OILS. 



The presence of light oils in the wood turpentines produced at 

 higher temperatures is the third possible difference. A crude tur- 

 pentine containing light oils may be so refined that the product will 

 be free from light oils (as in the case of crude No. 1), but the sepa- 

 ration is difficult and can not readily be made without some kind of 

 a fractionating column. If light oils are present in the crude tur- 

 pentine small quantities are likely to be in the refined turpentine. 



ROSIN OILS. 



The fourth possible difference between wood and gum turpentines 

 is difficult to describe, since it does not greatly affect the physical 

 properties expressed in the distillation curves. For instance, in the 

 analysis of refined turpentine No. 3 (fig. 33) it was quite noticeable 

 that the odor and color of all the fractions differed from similar frac- 

 tions of other turpentines. Except for the small amount of light 

 oils present (see p. 42) the peculiar odor and color apparently did 

 not tend to concentrate either in the first or last fractions, but were 

 distributed rather evenly throughout the distillate. These properties 



1 " The Distillation of Resinous Wood by Saturated Steam," Bulletin 109, Forest 

 Service. 



2 The absence of noticeable amounts of dipentene in turpentine No. 4 may be explained 

 from its source green sawmill waste ; that is, old, dead, lightwood or stumps may con- 

 tain dipentene while green freshly cut timber may not. It is expected that these de- 

 batable points will be settled by some work now under way in the Forest Products 

 Laboratory. 



