— 93 — 
With this formula of dihydropulegenone its behaviour is in perfect 
agreement. From it can be formed, not only the above formulated 
ketone acid CgHj^gOg, but also one of the formula: 
CH3 — CO — CH2 — CH2 — CH — CH (CHg)^ 
COOH 
which should further yield isopropyl glutaric acid. For pulegenone 
Wallach accepts in the first place formula I, as formula II agrees 
with that of camphorphorone, whose properties, however, do not corre- 
spond to those of pulegenone. On the other hand, dihydropulegenone, 
must be identic with dihydrocamphorphorone, — a matter which has 
been proved as a fact. 
Sesquiterpenes. With the study of sesquiterpenes Schreiner 
occupies himself in a number of essays^) which have been handed in 
as a thesis to the University of Wisconsin in June 1902. After a 
detailed historical retrospect of the discovery and classification of ter- 
penes in general, and more particularly of sesquiterpenes, the author 
discusses his division of these hydrocarbons into five classes (already 
previously published by him 2) according to the number of carbon- 
rings and of double linkings. This work is followed by a special part 
containing a detailed discussion of the individual representation of this 
class of bodies, their presence, and their physical and chemical behaviour. 
In Schreiner's opinion, the large number of the less exactly identified 
sesquiterpenes may probably be reduced to a small number of a few 
isomers, as was the case with the terpenes after Wallach 's pioneer's work. 
Caryophyllene. Up to the present, nothing was known of the 
constitution of caryophyllene, and of the hydrate formed from it by 
the addition of water according to Bertram's method. It may be 
concluded from the molecular refraction, that the molecule of the sesqui- 
terpene must contain at least two double linkings. Semmler^) now 
has recently selected both bodies as subjects for examination, and he 
has attempted to produce reduction-products of them. Caryophyllene 
cannot be reduced by sodium and alcohol. On the other hand, the 
hydrate, which this investigator considers a tertiary alcohol owing to 
its behaviour on oxidation with chromic acid mixture, is converted 
into a saturated hydrocarbon C^^ Hgg, when heated with zinc dust in 
a sealed tube. Its physical constants are as follows: 
b. p. 138° (19 mm); d^^o = 0,918; n^ = 1,4925- 
^) Pharm. Arch. 6 (1903), 24, 33, 56, 65, 81. 
2) Ibidem 4 (1901), 141, 164; Report April 1902, 85. 
3) Berichte 36 (1903), 1038. 
