THE PRODUCTION OF OIL OF 



WINTERGREEN 



BY 



HAROLD DAY FOSTER 



Forest Assistant, U. S. Forest Service. 



"T'HE "oil of wintergreen" of com- 

 * merce is the product of the dis- 

 tillation of an etherial oil. It was for- 

 merly obtained from the leaves of the 

 wintergreen or checkerberry (Gual- 

 theria procumbens, Linn.}. But the 

 production of the oil from this species 

 has been largely discontinued owing 

 to the great cost of gathering the plant 

 in sufficient amounts. Almost all of 

 the "natural oil" now on the market is 

 obtained from the sweet birch (Be tula 

 Icnta, Linn.}. 



This tree has a wide botanical dis- 

 tribution in the eastern United States, 

 but it is in the southern Apalachian 

 Mountains that it occurs at its best. 

 Here it is found as a timber tree of 

 some importance and is lumbered for 

 its wood which is used in the manu- 

 facture of furniture. The bark alone 

 is utilized in distilling the oil, and in 

 some regions where the tree does not 

 attain to sufficient size to make good 

 saw stock, or for local reasons there is 

 not a satisfactory market for the lum- 

 ber, the bark is peeled from the felled 

 trees which are then discarded. The 

 following notes on the distillation of 

 birch oil apply to the industry as it was 

 observed in McDowell county, North 

 Carolina : 



In this region the hardwood forests 

 are being lumbered and the merchant- 

 able trees of the many species which 

 occur here are being taken out. Some 

 birch lumber is sold to the furniture 

 trade, but as a rule birch is a poor 

 seller and only a few trees in this sec- 

 tion are large enough to make good 

 lumber. Distillation of the oil is car- 

 ried on by local residents. The lum- 

 ber company charges the distillers 20 

 cents for every tree cut, deducting this 



amount from the proceeds of the sale 

 of the crude oil. 



After felling the trees they are 

 peeled while green. It is essential that 

 the bark be green, for if it is allowed 

 to dry out before being used it be- 

 comes worthless for distilling pur- 

 poses owing to the rapid evaporation 

 of the etherial oil. The bark is 

 stripped from the trunk and stump and 

 the larger limbs, but the twigs and the 

 bark of the smaller branches are not 

 used. (See illustration No. I.) The 

 bark is brought to the distillery and 

 put on the floor around which there 

 is a narrow strip of lumber forming a 

 shallow box. Here it is chipped up 

 fine with axes. Everything about the 

 distillery and the methods of distilling 

 are simple to the point of crudeness. 



The distillery most commonly con- 

 sists of a floor on which the bark is 

 chipped, and one or more vats or stills 

 with their condensers, and these are 

 roofed over with a rude framework of 

 poles covered with hemlock bark. This 

 shed serves to protect the birch bark 

 from the drying sun, and the fires 

 from rain, as well as shielding the 

 workers from the weather (See illus- 

 tration No. II.) 



The stills are 3 feet wide by 4 feet 

 long and 3 feet deep. They are con- 

 structed of wood with cast iron bot- 

 toms and steam-tight tops or covers. 

 The still is placed in position on two 

 parallel rows of flat rocks one under 

 each side of the box, leaving a space 

 underneath on which fire is placed. 

 The smoke escapes through a vent 

 or low chimney of flat rock at the 

 rear. 



Inside the box and about 4 inches 

 above the iron bottom is a grating of 



