336 Wisconsin Academy of Sciences , Arts and Letters. 
Properties. 
Terpin hydrate crystallizes in large transparent prisms. 17 It is solu¬ 
ble in 250 p. of water, 10 p. alcohol, 100 p. ether, 200 p. chloroform; in 32 p. 
of boiling water and 2 p. of hot alcohol; 18 it is insoluble in petroleum 
ether. It melts at 116-117°, sublimating at the same time. When heated 
in a flask the water of crystallization is first given off with which a por¬ 
tion of the substance passes over, then the anhydrous terpin distills at 
258° . The anhydrous terpin congeals to a hard crystalline mass which 
melts at 102-105° . 20 
Terpin and its hydrate are saturated compounds 19 when boiled with 
acids or other dehydrating agents there results first of all the monatomic 
unsaturated alcohol tepineol, C 10 H 18 . Further dehydration yields ac¬ 
cording to the conditions and dehydrating agent employed, three hydro¬ 
carbons C 10 H 16 differing essentially in their properties: terpinene, 
terpinolene and dipentene. 21 Cineol also results, but only in small 
quantities 22 When treated with the hydrohalogen acids dipentene 
dihydrochloride, 23 dihydrobromide 24 and dihydriodide 25 result respec¬ 
tively. When treated with the chlorine, bromineand iodine derivatives 
of phosphorous the same dipentene derivatives result. 26 Hydrofluoric 
acids also acts upon terpin hydrate but the resulting products have not 
been studied 27 . With nitric acid it appears to yield an ether from which 
upon saponification the alchol can be regenerated only in part. 28 Nitric 
acid 29 also oxidizes terpin hydrate; permanganate solution 30 even more 
readily. 
Occurrence. 
In some text-books it has been stated that terpin hydrate has been 
found in the oil from Acimum basilicum, L., and in Cardamom oil. This 
however, is not at all to be considered as a natural occurrence. To our 
knowledge terpin hydrate does not occur in plant organs. 
Determination. 
Characteristic for terpin hydrate are its crystalline form and its melt¬ 
ing point, as also the melting-point of the anhydrous terpin. Chemically 
it can be characterized by converting it into any one of the dipentene- 
hydrohalogen derivatives. Of these the di-hydriodide can be prepared 
most readily. 31 
Methods of Formation. 
Hydration of— 
I. The hydrocarbons C 10 H 16 : 
(a) Limonene. 32 
(b) Pinene 33 (whereby inversion takes place.) 
II. The alcohol terpineol 34 C 10 Hi 8 O. As an indirect formation 
that from limonene monhydrochloride 35 may be con¬ 
sidered under terpineol. 
