LARCH (VENICE) TURPENTINE 275 



obtained is almost pure. The trunk of the tree is but Httle injured 

 by the tapping, and production, once it is begun, entails but little labor. 

 The same cavities, it is said, yield resin for twenty * to fifty ^ years. 



Because of its greater value Venice turpentine has been more care- 

 fully investigated than have the other varieties of turpentine. The 

 oleoresin was first examined by Berzelius.*' and others "^ have since 

 investigated it. The most comprehensive study is that by Tschirch 

 and Weigel,^ who showed it to contain 20 to 22 per cent of volatile oil, 

 composed mostly of pinene with some higher boiling sesquiterpene, and 

 V 5 to 80 per cent of resin, composed of laricinole acid, a and (5 larinolic 

 acids (possibly identical), and indifferent resinous residue. Rabak ^ 

 examined the oleoresin from /,. decidua (europae) grown in Wisconsin. 



More attention has been given, however, to the physical and chemical 

 constants than to the chemical constituents of the oleoresin. since these 

 are the values by which the quality of the product for commercial 

 purposes is determined. For the sake of comparison, values obtained 

 by various investigators are given later in this paper. 



For the years 1911 to 1914, inclusive, the average annual importation 

 of Venetian turpentine amounted to 92,026 pounds, but on account of 

 conditions in Europe, importation practically ceased in 1916. Experi- 

 ments were, therefore, begun by the Forest Service in the spring of 

 1917 to determine what the possibilities were of obtaining a similar 

 product from western larch (L. occidcntalis), wdiich occurs in large 

 stands in the Northwest. Holes were made in trees and plugged, as 

 described above, except that they were bored "breast-high." On three 

 areas on the National Forests in Montana trees were tapped between 

 May 22 and June 12, and collections of the oleoresin were made be- 

 tween October 15 and November 15. Single taps were made on thirty 

 trees on each area and double taps on twenty. The trees with double 

 taps yielded on the average nearly three times as much oleoresin as 

 did those with single taps. Table 1, compiled from the reports of the 



* Tschirch, "Die Harze und die Harzbehalter" (1906), p. 614. 

 ■' G. Planchon et E. Collin, "Les drogues simples d' origine vegetale, vol. 1, p. 70 

 'Lehrrbuch der Chemie, vol. vii (1838), p. 42. 

 'Tschirch, "Die Harze und die Harzbehalter" (1906), p. 614. 

 ^Archiv der Pharmacie (1900), p. 387; Proceedings of the American Pha 

 ceutical Association, vol. 49 (1901), p. 744. 



"Pharmaceutical Review, vol. 23 (1905), p. 44. 



rma- 



