The Limonene Group of Terpenes. 
357 
21 Ibidem, p. 271. The details of the dehydration experiments, p. 253. 
22 Ibidem, Bd. 239, pp. 18, 20, 23. 
23 Comp. Dipentene dihydrochloride: Historical notes. 
24 Observed first by Berthelot (Ann. Chim. Phys. [3] T 61, p. 463.) 
25 Comp. Dipentene dihydriodide: Historical notes. 
26 Oppenheim (1862). Annalen, Bd. 129, p. 149. 
27 Wallach, Ibidem, Bd. 239, p. 19. 
28 Ibidem. 
29 Ibidem, p. 20. 
Oxidizing terpin with nitric acid Hempel (Annalen, Bd. 180, p. 71) ob¬ 
tained besides carbonic and oxalic acids chiefly toluic acid, C 8 H 8 O , 2 
terephthalic acid and terebinic acid C 7 H ]0 O . 4 Oxidizing terpin with 
chromic acid he obtained terpenylic acid C 8 H 12 O 4 + H 2 O. Already in 
1856 Personne (Annalen, Bd. 100, p. 253) had obtained “Terebentilsaure 
C 16 H 10 O 4 by passing the vapor of terpin over hot soda-lime. 
30 Ibidem, Bd. 246, p. 267. 
31 Ibidem, Bd. 230, p. 249. 
32 Dissertation, p. 49 . 9 
33 The first reliable method is that of Wiggers. Tilden obtained the 
same product from American and French oil of turpentine. The hydra¬ 
tion takes place in the presence of acids: 
1. Of nitric acid — Wiggers, Mansfield. 
2. Of muriatic acid — Rammelsberg (Annalen, Bd. 52, p. 390.) 
[3. Of sulphuric acid—Tilden, Wallach.] 
34 That the regeneration of terpin hydrate from terpineol takes place 
within a few days in the presence of dilute acids was observed by Tilden 
and confirmed by Wallach (Annalen, Bd. 230, p. 266). 
85 Dissertation, p. 45. 
Oil. | Nitric Acid. | Alcohol. 
Wiggers. 
8 
9 /Sp. gravd 
4 ll.25-1.3] •• 
1 (80 p. c.).. 
(4 
1 (Commercial). 
3 (85 p. c.) ) 
Deville... 
Is 
2 (Commercial). 
6 (85 p. c.) | 
Hempel.. 
8 
o /Sp. grav.\ 
4 U.25—1.3] •• 
2 
(2y 2 
1 (Sp. gr. 1.4)... 
1 ) 
Tilden.... 
1 8 
3.5. 
3.5 ) 
Schmidt.. 
8 
2 (Sp. grav.\ 
Mi.is ] •• 
2 
Temp. 20-25°. Largest 
yield after 2 yrs. 1 oz. 
from 1 lb. oil. 
From 4 1. after G weeks 
250 g: abt. 7.2 p. c_ 
Tilden claims to have 
obtained a yield of 
abt. 33 p. c. 
Annalen 5 7,247. 
Ibidem, 71 , 348. 
(Ann. Chim. 
Phy. [3] 35,80.) 
Anna!enl80,73. 
J. C. S. 33, 248. 
Pharm. Chem. 
II., 818. 
