P _ : NOTES ON SCIENTIFIC RESEARCH. 73 
from alcoholic solutions in rhombohedric, pseudocubic crystals (1:1,2036), which, under 
pressure, form twins towards the three surfaces of the rhombohedron. On the other 
hand at least four different modifications are obtained from the melted camphor on 
crystallizing. When melted between two glass plates, cubic crystals form, which at 
97° become rhombohedric and exhibit but slight birefraktion. They form twin crystals 
like those obtained from alcoholic solutions. However, they are not identical with 
these, for small crystals appear at their borders which finally occupy the entire mother 
crystal and do not distinguish themselves in any way from it. The transformation is 
irreversible and takes place very slowly, but somewhat more quickly at increasing 
temperature. The rhombohedric crystals change at — 28° into likewise rhombohedric 
ones, but which are highly birefractive. . 
Wallerant also experimented with artificial camphor. Racemic camphor becomes 
cubic at 94°, probably owing to impurities, but even below — 27° it cannot be 
transformed into the highly birefractive crystals. 
Specific rotation of camphor in olive oil. 
The specific rotation of camphor in olive oil has been determined by H. Malosse’). 
For values of q between 75 and 95, it is as follows: — 
[é]pi0 = 57,9 — 0,53399 c + 0,02834 c? — 0,0005023 c?, 
[elpiso = 57,9 — 0,4894 p + 0,023805 p? — 0,0003867 p?, 
[@]pis0 = —139,69 + 7,3294 gq — 0,092205 gq? — 0,00038067 q?, 
when c represents the number of grams of camphor in 100 cc. of solution, 
p ” ” | ”) ” ” ” ” ” 100 grams ” ” 5) and 
q ” ” 7 ” ” ” olive oil DD) 100 ” ”) ” 
Malosse constructed a curve for the specific rotation of camphor in olive oil, 
from which it is to be seen that the specific rotation increases with the dilution. 
We would mention that many years ago already investigations were carried out 
as to the power of rotation which camphor shows in different solvents. Vogel, e. g.°), 
found that the specific rotation of camphor in isovaleric and capronic acids decreases 
at first in a very small degree, reaches a minimum and rises very considerably only if 
the solution is very strongly diluted. 
Rotation of camphor floating on water. 
The well-known phenomenon that small pieces of camphor vividly rotate when 
thrown on water, is explained by Marcelin*) through the solubility, though small, of 
camphor in water. The movement ceases as soon as the vessel, in which the camphor 
floats on water, is covered, if the solution is saturated, but starts again after removal 
of the cover. In consequence, the movement of the camphor would have to be ascribed 
almost exclusively to its being dissolved and only in a very small degree to its sub- 
limation. The thickness of the filmy camphor layer on the water equals the diameter 
of a camphor molecule. 
As to the behaviour of santenone when exposed to the light, see page 95. 
*) Bull. Soc. chim. WV. 15 (1914), 358. — 7%) H. Landolt, Das optische Drehungsvermégen. 2.4 ed. Braun- 
schweig 1898, p. 176. See also Reports October 1911, 123; October 1912, 159. — %) Annal. de Phys. 1X. 1 
(1914), 1; Chem. Zentralbl. 1914, 1. 1048. 
