RESULTS OF EXAMINATIONS. 17 



resulting tetrabromide, after several crystallizations from ethyl ace- 

 tate, melted at 104.5, the melting point of limonene tetrabromide. 



Totally anhydrous reagents, it was found, prevented the precipita- 

 tion of limonene tetrabromide. The limonene fraction dissolved in 

 glacial acetic acid and treated with bromine gave no trace of a crys- 

 talline precipitate after standing in a cool place for two days. When 

 a few drops of water were added, until a faint turbidity was produced, 

 a copious precipitate of limonene tetrabromide soon followed. 



Although this species is a variety of Pinus ponderosa, there are 

 marked differences in the properties of the two oils, as shown by 

 chemical analysis and inspection of the distillation curves (figs. 

 1,2, and 3). All the oils of Pinus ponderosa examined were Z-rota- 

 tory, while those of Pinus ponderosa scopulorum were cZ-rotatory. 

 The former consisted largely of /?-pinene and the latter of <*-pinene. 



EXAMINATION OF THE ROSIN. 



After digestion of the rosin on the steam bath with a mixture of 

 alcohol and concentrated hydrochloric acid, the crystalline residue 

 was recrystallized from 95 per cent alcohol and gave a yield of about 

 90 per cent of abietic acid. Purified by repeated crystallizations 

 from acetone, the abietic acid melted at 159. 



The original rosin, grade WW, had a specific rotation, [a] D = 

 30.95, determined from an 8.29 per cent alcoholic solution. The 

 purified crystals in an alcoholic solution gave the specific rotation 

 [a] D = -88.02 from the values: 



a=-1.36 ^ = 1.90 



1=1 d = 0.8132 



For further confirmation of the presence of abietic acid, the silver 

 salts were analyzed, with the following results: 



Per cent. 



0. 3203 gram silver salt gave 0.0834 gram silver =26. 04 



. 0600 gram silver salt gave .0159 gram silver =26. 50 



. 1922 gram silver salt gave .0504 gram silver =26. 22 



Mean =26. 25 



Silver abietate, Ag (C 20 H 29 O 2 ), requires 26.37 per cent silver. 



It will be noted that tliis abietic acid is strongly Z-rotatory, 

 and it is probable that the lower rotations of other authors is due 

 to a mixture of d- and I- acids. For the specific rotation of abietic 

 acid Dieterich 1 gives -48; Haller, 2 -53; Mach, 3 -69.96; Mead 

 and Kremers, 4 53.42; Leskiewicz 5 (for Z-sylvic acid), 102.85. 

 Caillot 6 observed, however, that the optical rotation decreased with 



1 Dissertation, Berne, 1883. < Proc. Am. Pharm. Ass'n, p. 198, vol. 41, 1893. 



2 Berichte, p. 2167, vol. 18, 1885. 5 j ou r. f. prak. Chem., p. 416, vol. 189, 1910. 



3 Monatsh. f. Chemie, p. 641, vol. 14, 1894. Bull. Soc. Chim., p. 387, vol. 21, 1874. 



58237 Bull. 11913 3 



