TheLimonene Group of Terrenes. 
335 
hand-books to-day. A critical study, however, must throw doubt upon 
at least some of their statements. Unfortunately time does not 
permit at present to verify these doubts by experimental evidence. 
Nevertheless, the same, as well as the reasons therefore, shall be men¬ 
tioned. If Blanchet and Sell’s contribution 13 be read in the light of our 
present knowledge of terpin hydrate several points will have to be re¬ 
garded in a rather doubtful light. The same is true of the historical 
sketch given by the editors of the “ Annalen.” It is even stranger that 
List could make the remark that the older analytical results corres¬ 
pond, whereas they fall very distinctly into two categories. An explana¬ 
tion for their views is probably to be found in the fact that at an early 
date terpin hydrate was converted into terpin free from water of crystal¬ 
lization, and that pinol hydrate, a substance approaching terpin closely 
in empirical composition had not been recognized as such. To make 
physical differences agree or to regard such differing statements as mis¬ 
prints may be admitted a single time, a repetition of such a procedure, 
however, must create suspicion. An attempt to bring all statements 
concerning the so-called “ terpentine oil hydrate” in harmoliy with actual 
facts would leave a number of points unexplained. This riddle, however, 
may be solved by substituting pinol hydrate in place of terpin (fre e 
from water of crystallization) whenever necessary. The following table 
may, therefore; serve as a key to a better understanding of the terpin- 
literature. 
Ci 0 H 20 O 8 
CioH 18 0 3 
Blanchet 
& Sell. 
Dumas & 
Peligot. 
Sten- 
house. 
Wiggers. 
Sobrero. ; 
69.76 
70.58 
C 
70.91 
• • • • 
• • • » 
• • • • 
69.99 
70.30 
. 
70.58 
11.62 
10.58 
H 
11.05 
11.68 
11.62 
10.58 
CO 
a. 
b. 
c. 
M 
63.15 
C 
63.8 
63.8 
64.0 
63.315 
63.25 
01 
H 
o 
11.57 
H 
11.4 
11.5 
11.4 
11.555 
11.56 
o 
Meltinar noint.... 
150° 
15 
0° 
* 
* Armstrong has shown recently that pinol hydrate prepared according to Sobrero 
melts at 150° (J. C. S , June, 1891, J. 317.) 
