248 
ME. C. GEEYILLE WILLIAMS OX ISOPEEXE AXD CAOrTCHIXE. 
The reduplication of a formula has not the same relative influence upon the boiling- 
point of amylene that it has upon that of isoprene ; thus — 
Paramylene, boils at 160' 
Amylene, C*® H'®, boils at 39' 
Difference . . .121 
Caoutchine, C^®H‘®, boils at 171° 
Isoprene, C'®H®, boils at 37° 
DiflTerence . . .134 
Oil of turpentine boils at 160°, and is taken as the pivot round which the boiling- 
points of hydrocarbons should arrange themselves at distances proportioned to the num- 
ber of atoms of carbon and hydrogen in then’ formulae ; yet caoutchine, vrhich not only 
has the same formula, but gives almost identical reactions, boils at 171°, eleven degrees 
higher, and very near that of carvene, which is 173°. 
Comparative experiments on the Action of Bromine on Caoutchine and Oil of Turpentine. 
M. Himlt had observed that chlorine and bromine act upon caoutchine, and that 
the products when distilled over a base afibrded an oil containing less hydi’ogen than 
caoutchine. He did not examine the nature of the reaction more closely. 
I mentioned at the commencement of this paper that I had several years ago made 
an experiment on the mutual action of bromine and caoutchine, which led me to beheve 
the latter to belong, not to the olefiant, but to the vast group of hydrocarbons isomeric 
with oil of turpentine. But that experiment hawng been made with the bromme and 
hydrocarbon undiluted, and, moreover, the caoutchine not having been prepai'ed by 
myself, I considered it necessary to repeat it with several precautions not then observed. 
The action of bromine upon the terebenes is peculiar, one atom, or four-volume equi- 
valent, always requiring exactly foui’ atoms of bromine to produce a colourless fluid. If 
the hydrocarbon and the bromine be diluted, the former uith alcohol, the latter with 
water, the experiment may be made with considerable precision. For the purpose of 
comparing the isomers, I prepared some freshly dried and rectified turpentine and 
caoutchine. They were diluted with sutflcient alcohol for each of the resulting fluids 
to contain exactly ten per cent, of hydrocarbon. The bromine employed was in the 
state of a weak solution in water, twenty cubic centimetres containing 0‘2527 of bromine. 
A small flask containing twenty cubic centimetres with the stopper in its place, was 
employed each time to measure the bromine water, which was transferred to a large 
stoppered flask, every precaution being taken to prevent loss. The diluted hydrocarbon 
was then gradually dropped into the bromine water from a Schiister's alkalimeter con- 
taining a weighed quantity. Considerable agitation Avas applied after each addition. 
When the bromine water Avas nearly decolorized, the liquid Avas added very cautiously, 
and an interval of about half a minute allowed to elapse betAveeii each addition. Allien 
the fluid had become perfectly colourless, the alkalimeter Avas reAveighed. The folloAv- 
ing numbers were obtained in eight experiments made in the manner described: — 
