2 BULLETIN 129, U. S. DEPARTMENT OF AGRICULTURE. 



three trees was distilled. Further, the average yields from the heart- 

 wood l of several trees were in a few instances compared with the 

 yields from lumber of the same species. Differences in yields may 

 also occur in trees of the same species grown in different localities, 

 and for this reason the results obtained are averaged separately when 

 more than one locality is represented. At least two distillations 

 were made of each kind or form of material tested. 



Different forms of wood such as body wood (wood free from bark) , 

 slabs, limbs, etc. were distilled, but the proportion of each used in 

 commercial practice varies with different plants and localities, so that 

 it is not possible to assume a proportion representing average con- 

 ditions. For this reason the yields from different forms of wood of 

 the same species are presented separately. The corresponding yield 

 per given weight of wood, made up of any proportion of the various 

 forms, can readily be calculated. However, as a basis of comparison 

 between the species, the average yields from all heartwood runs (in- 

 cluding lumber) are taken arbitrarily as the species value. The mean 

 of the heartwood and stab-wood yields is also given wherever both 

 forms were distilled. 



THE RETORT. 



Figure 1 shows the construction of the retort in which the distilla- 

 tions were made. The retort proper A was surrounded by the oil 

 jacket B, which was filled with a high-flash-test cylinder oil. The 

 outlet pipe C connected the retort with an ordinary worm condenser 

 (not shown). The pyrometer tubes, 1, 2, 3, 4, and 5. made it possible 

 to measure the temperature at various places within the retort. The 

 retort was mounted on an iron stand, was insulated on all sides, and 

 heated by a row of gas burners underneath. The flames from the 

 burners played chiefly up one side of the cylinder and induced a fairly 

 good circulation of the hot oil around the retort. 



PREPARATION OF MATERIAL. 



The forms of material used varied to some extent with different 

 species, but most of them consisted of round bolts. These were sawed 

 into slabs and heartwood in about the same proportion as would occur 

 in ordinary sawmill practice, and the percentage of bark on the slabs 

 was roughly determined. Sticks were prepared from 6 to 8 square 

 inches in cross section and a trifle less than 18 inches long. Just before 

 each charge of wood was weighed, six 1-inch sections, each cut from 

 a different stick and in each case from a different part of the stick, 

 were taken for moisture determinations. 



In the comparative distillations on bark and sapwood the material 

 was taken from the same bolts. When limbs were used they weie 



1 The term ' ' heartwood " as used in this paper applies to the material left after the slabs have been removed 

 from a bolt or log. It was in all cases entirely free from bark, but small amounts of sapwood sometimes 

 remained. Lumber is considered as made from heartwood as thus defined. 



