132 Journal of the Mitchell Society {^Decemher 



with an investigation carried out in this laboratory in collabora- 

 tion with the United States Forest Service, there remained a 

 large number of specimens of resin from well identified individ- 

 ual trees growing in Florida. It seemed desirable, therefore, to 

 study more closely the question of the proportions of resene in 

 these specimens. The investigation was extended to the resins 

 of conifers growing near this laboratory, and to specimens col- 

 lected in other countries. Finally the amount of resene was 

 determined in several oleoresins obtained in perfectly fresh 

 condition from individual trees in Florida. These specimens 

 were collected from the two species of pines from which crude 

 turpentine is commercially obtained in this country. Firms 

 Palustris (Longleaf Pine), and Pinus Hetrophylla (Cuban or 

 Slash Pine). 



The resins were obtained by distilling the oleoresins in a cur- 

 rent of steam slightly superheated, the temperature being raised 

 to 140*^ C. toward the end of the distillation. After complete 

 removal of the volatile oil, the residue was kept at 140^ C. in 

 the oil bath surrounding the distillation flask until all water was 

 driven off. The molten resin was then filtered through absorbent 

 cotton and cooled to solidification in glass or iron molds. 



The determination of resene in the resins was carried out in 

 the usual manner. The weighed specimen, about two grams, 

 was dissolved in a considerable excess of N'^2 alcoholic potas- 

 sium hydroxide, allowed to stand at room temperature eighteen 

 hours, diluted with water until separation of the resene began 

 and the solution cleared by the addition of a small quantity of 

 ninety-five per cent, alcohol. This solution was then extracted 

 three times with petroleum ether, boiling below 40 °c. The com- 

 bined extracts were shaken out with fifty per cent, alcohol to 

 remove slight amounts of dissolved potassium salts of resin 

 acids. After drawing off the petroleum ether extract into a 

 weighed glass evaporating dish, it was allowed to evaporate 

 spontaneously to constant weight. 



In the case of the oleoresins, after spontaneous evaporation 

 of most of the petroleum ether, the residue was heated for five 

 hours on a steam bath in order to remove completely the petro- 



