202 J. M. Blake on natural Hydrated Terpin. 
Art. XXIII.—On the crystallization of natural Hydrated Terpin 
from California ; by JouN M. BLAKE. 
Some crystals, from a buried pitch-pine log, were handed me 
for examination by Prof. S. W. Johnson, of the Sheffield Scien- 
tific School. 
A comparison of these crystals with terpin of artificial prep- 
aration leaves no doubt that the natural substance is hydrate 
turpentine camphor. The natural and artificial crystals agree 
closely in their angles, and have the same cleavage. The posi 
tion and separation of the optical axes is alike in both, and ex- 
periment shows that the two substances are supercrystallizable. 
Certain observations made at first, suggested that the two spe- 
cimens might not be absolutely identical, but rather isomeric hy- 
drates, such as were supposed by Berthelot to result from iso- 
meric oils, derived from the same or different trees. Thus, hemi- 
edrism constantly occurred on the natural crystals, which has 
not been observed on the artificial. The proportional develop- 
ment of the planes was strikingly different. The two specimens 
manifested opposite pyro-electrie characters, in so far that the 
free-growing extremities of the natural crystals were antilogue 
poles, (developed negative electricity on heating,) while those of 
the artificial crystals, first examined, were the reverse, or ana- 
logue poles. 
On further investigation, these points of difference disappeared. 
By recrystallizing from alcohol and other solvents, much varla- 
tion was produced in the planes. The peculiar development of 
the natural crystals was not indeed reproduced on the artificial, 
but the attachment of the latter to the support by the analogue 
saa as with the natural crystals, was obtained. On recrystal- 
izing from alcohol, natural terpin lost its hemihedral charac: 
ter, and in case of crystals grown radiating from a support, 
sented the analogue pole to the solution, like the artificial 
stance when deposited from the same solvent. Crystals of each, 
when free-growing in alcoholic solution, had the same develop- 
ment of the planes, and with each there was the same percept- 
ble difference in the proportions of the planes at the two ends of 
a crystal, by which the poles could be distinguished; but 20 
corresponding difference could be detected in the angles of these 
terminal planes. 
pre- 
sub- 
hag eR NR ripe ae erg WN Retin Sy Oe pe ee ND aren nar oe Seat ee 
