88 
Journal of the Mitchell Society [ November 
predominating species and Long attributed to this fact the dextro- 
rotatory character of American spirits of turpentine. This view 
has been generally accepted. 
The fact that spirits of turpentine is frequently adulterated with 
optically inactive mineral oil, led A. McGill 2 to make a large num- 
ber of determinations of the rotation of commercial samples of 
spirits of turpentine, in the hope of utilizing this property for the 
detection of adulteration. From the widely varying results 
obtained he was compelled to declare the method useless. 
New evidence upon this point has been obtained from investiga- 
tions carried on in this laboratory in collaboration with the U. S. 
Forest Service, the experimental work having been carried out by 
Messrs. George A. Johnston and W. S. Dickson under the direc- 
tion of the writer. In order to gain a better knowledge of the 
oleoresins from the two principal species of pine utilized in the 
turpentine industry at the present time, fourteen trees were 
selected on a Florida turpentine farm. One-half of these were 
Firms palustris , the other half Pinus heterophylla. Three trees of 
each species were tapped for the first time at the beginning of the 
experiments. In each case a small, young pine, a medium pine, 
and a large, old pine were selected. In another set four trees 
were selected, two each Pinus palustris and Pinus heterophylla. 
These trees had been subjected to turpentining during the pre- 
vious year; the chipping or weekly scarification, on all of them 
having been unusually shallow, only about one-half as deep as is 
commonly practiced. In a third set four trees were selected, two 
of each of Pinus palustris and Pinus heterophylla , which had been 
turpentined during the previous year, and on each of these the 
depth of the chipping was the normal cut. The trees in each set 
were chipped at intervals of seven days. 
Special precautions were taken in the collection of the oleore- 
sins. The cup and gutter system described in Bulletin No. Ifi, 
U. S. Bureau of Forestry , was used. Instead of the clay cup com- 
monly used, oyster pails were substituted. The entire apparatus 
was covered with black oilcloth fastened securely into the bark of 
the tree above the chipping surface, thereby protecting the resin 
2 Bulletin No. 79, Inland Revenue Dept., Canada. 
